Influenza Situation Updates 2023

Dengue Situation Update 679 │ 1 Dengue Situation Update 679 31 August 2023 Update on the Dengue situation in the Western Pacific Region This report describes the epidemiology of dengue in the World Health Organization Western Pacific Region. Data are compiled from open sources (national indicator-based surveillance systems) with the exception of Cambodia, Lao People’s Democratic Republic, Viet Nam, and the Philippines, where data are provided from WHO Country Offices, and for Pacific Island Countries, where syndromic surveillance data are provided by the Division of Pacific Technical Support. Information is reported based on countries’ standard dengue case definitions and a summary of these definitions and countries’ dengue surveillance systems is included as an annex to this report. Due to differences in surveillance methods and reporting practices, a comparison of trends between countries and areas is not possible however national trends can be observed over time. Northern Hemisphere Cambodia As of epidemiological week 33 of 2023, a total of 16,140 cases with 32 deaths (Case Fatality Rate (CFR) 0.20%) were reported to the National Dengue Surveillance System in Cambodia since 1 January 2023 (Figure 1); an increase compared to 6,140 cases and 11 deaths (Case Fatality Rate (CFR) 0.17%) reported in 2022 over the same period. Figure 1: Dengue cases reported weekly in 2023 vs Mean and Mean+2SD during 2015-2020 *excluding 2019 in Cambodia; Source: National Dengue Surveillance System (NDCP/CNM/MOH) ^ Dengue Situation Update 679 │ 2 China In July 2023, 1604 dengue cases were reported in China. There have been a total of 1708 dengue cases and no deaths in the country from January 2023 to July 2023 (Figure 2). Figure 2: Dengue cases reported monthly from 2015-2023 in China Source: National Health Commission, China Lao People’s Democratic Republic In epidemiological week 33 of 2023, 1594 dengue cases and no deaths were reported (Figure 3). The number of reported cases is lower than the numbers reported in epidemiological week 32 (1705 cases with two deaths). The cumulative number of cases reported in 2023 (as of epidemiological week 33) is 19,712. This is a 12.4% increase compared to the 17,545 cases reported during the same period in 2022. There have now been 14 deaths reported in 2023. Figure 3: Dengue cases reported weekly from 2018-2023 in Lao PDR Source: National Centre for Laboratory and Epidemiology, Ministry of Health, Lao PDR Dengue Situation Update 679 │ 3 Malaysia During epidemiological week 33 of 2023, there were 2,248 dengue cases, compared to 2,487 cases in the previous week (Figure 4). One dengue-related deaths were reported in week 33. The cumulative number of dengue cases reported to date is 75,928 cases, a 115% increase compared to 35,330cases for the same period in 2022. As of epidemiological week 33, a total of 54 deaths due to dengue have been reported, compared to 22 deaths for the same period in 2022. Figure 4: Dengue cases reported weekly from 2022, 2023, and median 2018-2022 in Malaysia Source: Department of Health, Malaysia Philippines There have been no update since the previous report. During epidemiological week 28 of 2023, there were 132 new dengue cases reported (Figure 5). As of 15 July 2023, a total of 80,318 dengue cases have been reported. The number of cases is 17% lower compared to the same period in 2022 (n=96,500). From 1 January to 15 July 2023, there have been 299 deaths (CFR 0.42%), which is lower than the 405 deaths (CFR 0.42%) reported in the same period in 2022. Figure 5: Dengue cases reported weekly from 2022 and 2023 in the Philippines Source: Department of Health, the Philippines (Note: there is a 3-4 week systematic delay in reporting and numbers should be interpreted with caution) N u m b er o f ca se s Dengue Situation Update 679 │ 4 Singapore As of epidemiological week 34 of 2023, 199 dengue cases were newly reported in Singapore, leading to a total of 5,956 cases (Figure 6); This is lower than the same period (epidemiological weeks 1–34) in 2022, when a total of 25,516 cases were reported. Preliminary results of all positive dengue samples serotyped in August 2023 showed DEN-1, DEN-2, DEN-3, and DEN-4 at 52.7%, 24.7%, 11.0%, and 11.6% respectively. Figure 6: Dengue cases reported weekly from 2018-2023 in Singapore Source: Communicable Diseases Division, Ministry of Health, Singapore (Note: Case numbers are derived from the MOH Singapore’s Weekly Infectious Bulletin Year Excelsheet as available from MOH | Weekly Infectious Diseases Bulletin) Viet Nam As of 20 August 2023 (epidemiological week 33), cumulatively 66,386 dengue cases including 14 deaths were reported in Viet Nam, which is a decrease by 61.5% compared to the same period in 2022 (172,567 cases including 93 deaths). During epidemiological week 33 (from 14 August to 20 August), 4,325 cases including no death was reported, a 6.8% increase in cases compared to the previous week (4,051 cases). Of the cases, 3,194 were hospitalized, a 5% increase compared to the previous week (3,041 hospitalizations) (Figure 7). Figure 7: Number of dengue hospital admissions and deaths by weeks in 2022 compared to 2023, as of week 31 2023, Viet Nam Source: General Department of Preventive Medicine, Ministry of Health, Viet Nam Note hospitalizations include inpatients and outpatients The alert threshold is a 5-year mean plus 2 standard deviations Dengue Situation Update 679 │ 5 Southern Hemisphere Australia There have been no updates since the previous report. There were 37 dengue cases reported in Australia during the reported fortnight (10 July to 24 July 2023). As of 24 July 2023, the cumulative number of dengue cases is 490. The number of cases for this reported fortnight was higher at 37 cases for the current year, compared to the 15 cases reported in same period in 2022. The number of cases reported in July 2023 was higher than the reported number of cases for same month in the years 2020-2021 (Figure 8). This may be attributed to COVID-19-related travel restrictions in 2020-2021. Before COVID-19, Australia had seen notifications of overseas-acquired cases from travelers returning from dengue-endemic areas. Figure 8: Laboratory-confirmed dengue cases reported monthly from 2015-2023 in Australia Source: Department of Health, Australia Note: Graph was updated on 8 August 2023 Pacific Islands Countries New Caledonia From 1 January to 31 July 2023, four confirmed dengue cases were reported in New Caledonia (Figure 9). This is higher compared to the same period in 2022 when a total of one dengue case was reported. Of the four confirmed dengue cases in 2023, two were imported cases. The serotype of the two imported cases were DENV-1 and DENV-2. Figure 9: Dengue cases reported by week from 2021 to 2023 in New Caledonia Source: Network of sentinel physicians, New Caledonia Dengue Situation Update 679 │ 6 Pacific Island Countries and Areas (PICs) – Dengue-like illness (DLI) Surveillance During epidemiological week 33 of 2023, many Pacific Island Countries and Areas with available surveillance data (17/18 PICs) reported no or low numbers of DLI cases. Solomon islands have reported a significant decrease in DLI cases from week 30 to week 33, while increases in DLI cases have been reported in Micronesia (Federated States of) from week 27 to week 32. Both Micronesia (Federated States of) and Solomon Islands have reported higher number of cases compared to the same period in 2022. 0 5 10 15 20 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Cook Islands DLI Trend - 2021 -2023 (WK 33) DLI 2023 DLI 2021 DLI 2022 0 200 400 600 800 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Fiji DLI Trend - 2021 -2023 (WK33) DLI 2023 DLI 2021 DLI 2022 Baseline 0 20 40 60 80 100 120 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 C as e s Epi week French Polynesia DLI Trend - 2021 -2023 (W33) DLI 2023 DLI 2021 DLI 2022 0 2 4 6 8 10 12 14 16 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 C as e s Epi week FSM DLI Trend - 2021 -2023 (W33) DLI 2023 DLI 2022 DLI 2021 0 2 4 6 8 10 12 14 16 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Kiribati DLI Trend - 2021 -2023 (WK33) DLI 2023 DLI 2021 DLI 2022 0 1 2 3 4 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 ca se s Epi week Marshall Islands DLI Trend - 2021 -2023 (WK33) DLI 2023 DLI 2021 DLI 2022 Dengue Situation Update 679 │ 7 0 2 4 6 8 10 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week N Mariana Is DLI Trend - 2021 -2023 (WK33) DLI 2023 DLI 2021 DLI 2022 0 1 2 3 4 5 6 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 ca se s Epi week New Caledonia DLI Trend - 2021 -2023 (WK33) DLI 2023 DLI 2021 DLI 2022 0 2 4 6 8 10 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 ca se s Epiweek Niue DLI Trend - 2021 -2023 (WK33) DLI 2021 DLI 2022 DLI 2023 0 2 4 6 8 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 ca se s Epiweek Palau DLI Trend - 2021 -2023 (WK33) DLI 2023 DLI 2021 DLI 2022 0 2 4 6 8 10 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 ca se s Epi week Pitcairn Islands DLI Trend - 2021 -2023 (WK33) DLI 2021 DLI 2022 DLI 2023 0 5 10 15 20 25 30 35 40 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 ca se s Epi week Samoa DLI Trend - 2021 -2023 (WK33) DLI 2023 DLI 2021 DLI 2022 0 20 40 60 80 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Solomon Islands DLI Trend - 2021 -2023 (WK33) DLI 2023 DLI 2021 DLI 2022 0 2 4 6 8 10 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 C as e s Epiweek Tokelau DLI Trend - 2021 -2023 (WK33) DLI 2021 DLI 2022 DLI 2023 Dengue Situation Update 679 │ 8 Figure 10. Reported cases of dengue-like illness in Pacific Islands Countries and Areas Source: WHO Division of Pacific Technical Support Note: Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System (PSSS). Furthermore, the syndromic case definition of DLI may capture cases with non-dengue acute febrile illnesses (AFI) with similar clinical manifestations to dengue. This includes AFI such as chikungunya, influenza, hantavirus, leptospirosis, malaria, measles, paratyphoid and typhoid fevers, scrub typhus, yellow fever, zika, other diseases. The PSSS may also capture dengue cases under ‘prolonged fever’ surveillance. Alert threshold for DLI is twice the average number of cases seen in the previous 3 weeks. FSM: Federated States of Micronesia 0 2 4 6 8 10 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 C as e s EPI week Tuvalu DLI Trend - 2021 -2023 (W33) DLI 2021 DLI 2022 DLI 2023 0 2 4 6 8 10 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Tonga DLI Trend - 2021 -2023 (WK33) DLI 2023 DLI 2021 DLI 2022 0 10 20 30 40 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 ca se s Epi week Vanuatu DLI Trend - 2021 -2023 (WK33) DLI 2023 DLI 2022 DLI 2021 0 2 4 6 8 10 12 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s EPI Week Wallis & Futuna DLI trend -2021 -2023 (WK33) DLI 2023 DLI 2021 DLI 2022 Dengue Situation Update 679 │ 9 Annex 1. Summary of dengue case definitions, laboratory sampling and testing methods used for surveillance in Member States as of 2023 Country Case definition Surveillance system Laboratory sampling and testing method Reference Clinically confirmed case Laboratory confirmation required Description Australia Fever, headache, arthralgia, myalgia, rash, nausea and vomiting Yes Dengue is a nationally notifiable disease and cases are monitored through the National Notifiable Diseases Surveillance System (NNDSS) indicator-based surveillance system. Both confirmed and probable cases are nationally notifiable. A confirmed case requires both laboratory definitive evidence and clinical evidence. A probable case requires either laboratory suggestive evidence and clinical evidence and epidemiological evidence, or clinical evidence and household epidemiological evidence. Laboratory definitive evidence: - Isolation of dengue virus, or - Detection of dengue virus by nucleic acid testing, or - Detection of NS1 antigen in the blood by EIA, or - IgG seroconversion or significant increase in antibody levelor fourfold or greater rise in titre to dengue virus (proof by neutralization or another specific test) Laboratory suggestive evidence: - Detection of NS1 antigen in blood by rapid antigen test, or - Detection of dengue virus-specific IgM in blood Epidemiological evidence: - Exposure between 3 – 14 days prior to onset either in a country with known dengue activity or in a dengue-receptive area in Australia where a locally-acquired or imported case has been documented with onset within a month. Household epidemiological evidence: - Living in the same house as a locally- acquired case in a dengue-receptive area of Australia within a month of onse in the case and at least one case in the chain of epidemiologically linked cases is laboratory confirmed. 1 Dengue Situation Update 679 │ 10 Cambodia Suspected dengue: very high fever at 39-40 degrees celcius for 2-7 days (usually 3-4 days), with 2 or more of the following signs: flushed face, headache, retro-orbital pain, myalgia/arthralgia, cutaneous rash, haemorrhagic signs (petechiae, positive tourniquet test), and leucopenia. Probable dengue: signs of suspected dengue plus laboratory test results (see right column)) or that the case occurred in an area where the dengue case has been confirmed. Yes National Dengue Control Program (NDCP) enhanced sentinel surveillance system Communicable Disease Control (CDC) syndromic surveillance system (CamEWARN). Health Management Information System (HMIS) collects data on confirmed cases and deaths. Data collected for Cambodia Laboratory Information System (CamLIS), comprised of 32 participating hospital laboratories where NS1 detection is conducted. Laboratory testing: Antibody HI>= 1/1280 or IgM/IgG positive by ELISA test in convalescence serum 2 China (i) more than two symptoms of acute onset fever, severe headache, orbital pain, myalgia, arthralgia, fatigue with a history of travel in a dengue endemic area within 15 days before symptom onset or cohabitation with an individual with confirmed dengue; or no travel history, but with a rash or positive tourniquet test AND leucopenia or thrombocytopenia or serum IgM positivity. No Reported to the Chinese Centre for Disease Control and Prevention (China CDC) through the Chinese National Notifiable Infectious Disease Reporting Information System (CNNDS). Laboratory confirmation is done by real-time RT-PCR, NS1 in acute-phase serum, or virus isolation from an acutely infected patient’s serum. WHO internal communication Lao People's Democratic Republic WHO dengue case classification (2009) † No National Surveillance System for Notifiable Selected Diseases, indicator-based surveillance system that consists of passive weekly reports of clinically suspected cases, on admission, from all health-care facilities across the country. 3 Malaysia WHO dengue case classification (2009) † Yes National Dengue Surveillance System, indicator-based surveillance system All suspected cases are to be tested by the following laboratory tests: Rapid Combo Test (RCT) (NS1, IgM, IgG), Dengue Antigen and Serology tests by ELISA, Dengue Viral RNA Detection (Real time RT-PCR), Viral Isolation 4 Philippines WHO dengue case classification (2009) † Yes Philippine Integrated Disease Surveillance and Response (PIDSR), indicator-based surveillance system. Reporting delays of 2-3 weeks, making comparison of current weekly and cumulative figures with previous years difficult. Confirmed dengue is a suspect case with positive (+) viral culture isolation and/or PCR. NS1 (+), IgM is used to identify probable dengue. 5, 6, 7 Singapore (endemic) Fever, headache, backache, myalgia, rash, abdominal discomfort and thrombocytopenia and laboratory testing (see right column) No Dengue is a legally notifiable disease in Singapore and notifying the Ministry of Health should not be later than 24 hours from the time of diagnosis. Laboratory confirmation is done using standard diagnostic tests for the detection of dengue NS1 antigen, IgM and IgG, or RT-PCR. 8,9 Dengue Situation Update 679 │ 11 Viet Nam (endemic) Acute onset of fever continuously lasting from 2-7 days AND at least 2 of the following: haemorrhagic manifestation /presentation; headache, loss of appetite, nausea, vomiting; rash; muscle pain, joint pain, orbital pain; lethargy; abdominal pain. No As per the MOH dengue surveillance guideline, in routine surveillance MAC-ELISA is conducted for at least 7% and virus isolation is conducted for at least 3% of clinical cases. In an outbreak, at least 5 to 10 suspected cases are tested. 10 Pacific Island Countries WHO dengue case classification (2009) † No Pacific Syndromic Surveillance System Confirmed case: Isolation of dengue virus or detection of dengue-specific antigen or antibodies in tissue, blood, CSF or other body fluid by an advanced laboratory test 11 Only the minimum criteria required for fulfilling a clinical dengue case definition are included here; additional signs and symptoms required for more severe forms are not listed. † A probable dengue case is defined as any case living in or travel to dengue endemic area with fever and two or more of the following: nausea, vomiting, rash, aches and pains, positive tourniquet test, leucopenia and any warning sign. A case with warning signs is defined as a clinically diagnosed case with any of the following: abdominal pain or tenderness, persistent vomiting, clinical fluid accumulation, mucosal bleed, lethargy, restlessness, liver enlargement > 2 cm and increase in haematocrit concurrent with rapid decrease in platelet count. Severe dengue is defined as severe plasma leakage leading to any of the following: shock, fluid accumulation with respiratory distress OR severe bleeding as evaluated by clinician OR severe organ involvement of liver (aspartate amino transferase or alanine amino transferase ≥ 1000), central nervous system (impaired consciousness) or heart and other organs.10 References: 1. Australian Government Department of Health AGDo. Dengue virus infection surveillance and case definition [updated 14 June 2022 and 1 January 2018 respectively] Available from: https://www.health.gov.au/diseases/dengue-virus-infection, and https://www.health.gov.au/sites/default/files/documents/2022/06/dengue-virus-infection-surveillance-case-definition.pdf 2. Cambodia Ministry of Health NCfP, Entomology and Malaria Control. National Guideline for Clinical Management of Dengue, 2018. 2018. Available from: https://niph.org.kh/niph/uploads/library/pdf/GL055_National_guideline_for_ClM_Dengue.pdf. 3. Khampapongpane B, Lewis HC, Ketmayoon P, Phonekeo D, Somoulay V, Khamsing A, et al. National dengue surveillance in the Lao People's Democratic Republic, 2006-2012: epidemiological and laboratory findings. Western Pac Surveill Response J. 2014;5(1):7-13. Available from: https://www.ncbi.nlm.nih.gov/pubmed/24734212. 4. Ministry of Health Malaysia DCD. Case definitions for infectious diseases in Malaysia. 2017. Available from: https://www.moh.gov.my/moh/resources/Penerbitan/Garis%20Panduan/Pengurusan%20KEsihatan%20&%20kawalan%20pykit/Case_Definition_Of_Infectious_Disease_3rd_Edition_2017.pdf 5. Secretary PDoHOot. Guidelines for the Nationwide Implementation of Dengue Rapid Diagnostic Test (RDT), Administrative order No.2016-0043. 2016(2016-0043). 6. Secretary PDoHOot. Revised Dengue Clinical Case Management Guidelines 2011, Administrative order No.2012-0006. 2012 22 March 2012. Report No. 7. Diseases SNCfI. Diseases and Conditions, Dengue 2020 [updated 14 September 2020. Available from: https://www.doh.gov.ph/Health-Advisory/Dengue. 8. National Centre for Infectious Diseases, Dengue. Available from: https://www.ncid.sg/Health-Professionals/Diseases-and-Conditions/Pages/Dengue.aspx 9. National Environment Agency. Surveillance and Epidemiology Programme [updated 21 April 2023]. Available from: https://www.nea.gov.sg/corporate-functions/resources/research/surveillance-and- epidemiology-programme#Ehi%20Diagnostics%20Unit 10. Viet Nam Ministry of Health VNMo. Circular 54/2015 / TT-BYT 2015 [updated 26 April 2016. Available from: https://syt.thuathienhue.gov.vn/?gd=27&cn=108&tc=3993. 11. Pacific Islands Outbreak Manual. Available from: https://www.pphsn.net/resources/outbreak-manual/ 12. WHO dengue outbreak toolbox. Available from: https://www.who.int/docs/default-source/outbreak-toolkit/updates-documents_july-5/dengue-outbreak-data-collection-toolbox---inis-3-july- 1.pdf?sfvrsn=ec3ffcf3_2

Bi-weekly Influenza Situation Update 4 January 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 51 of 2022 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported from week 1 to week 51 of 2022 have been Influenza A (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1, 2022 to week 51, 2022 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, week 51, 2021 to week 51, 2022 (Source: WHO FLUNET) Country (most recent week of report) Total number of specimens processed Total number of influenza positive specimens Australia (51 of 2022) 277,307 11,868 Cambodia (49 of 2022) 5,680 401 China (50 of 2022) 511,907 56,356 Fiji (47 of 2022) 1,545 210 Japan (50 of 2022) - 72 Lao People’s Democratic Republic (51 of 2022) 4,932 629 Malaysia (51 of 2022) 35,472 4,867 Mongolia (46 of 2022) 5,105 273 New Caledonia - - New Zealand - - Papua New Guinea - - Philippines (51 of 2022) 3,126 201 Republic of Korea (51 of 2022) 8,350 295 Singapore (51 of 2022) 7,659 890 Viet Nam (41 of 2022) 165 43 Influenza Situation Update | 2 Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza acitivity is similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 51 of 2022, sentinel hospitals in the northern provinces reported an ILI% of 8.3%, an increase from the previous week's level of 6.2% and higher than the same weeks in 2019 to 2021 (5.3%, 2.8% and 3.9%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in Northern China, 2019-2022 (Source: China National Influenza Center) Influenza Situation Update | 3 Mongolia During week 51 of 2022, the ILI activity in Mongolia decreased to 74 ILI cases per 10,000 population. This is higher than the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2022 (Source: Mongolia National Influenza Center) Republic of Korea In week 51 of 2022, the overall weekly ILI rate was 41.9 ILI cases per 1,000 outpatient visits, which is higher than the previous week (30.3 per 1,000 outpatients) (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2017-2022 (Source: Korean Centres for Disease Control and Prevention) ILI (p er 1 ,0 00 O ut pa tie nt C on su lta tio ns ) Influenza Situation Update | 4 Sentinel influenza surveillance Japan In week 49 of 2022, the number of cases reported weekly by sentinel hospital sites remained very low in Japan. The number of cases in 2022 has been consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2012-2022 (Source: Japan National Institute of Infectious Diseases) Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed that the overall seasonal influenza activity in Hong Kong remained low. In week 51, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 0.3 ILI cases per 1,000 consultations, which was lower than 0.6 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 30.4 ILI cases per 1,000 consultations, which was higher than 29.1 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2022 Figure 7: ILI consultation rates at sentinel private doctors, Hong Kong SAR 2018-2022 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) Influenza Situation Update | 5 China (South) - ILI Surveillance During week 51 of 2022, the percentage of visits for ILI at national sentinel hospitals in Southern China was 13.0%, higher than the last week (9.3%) and higher than the same week of 2019-2021 (5.7%, 3.4% and 4.0%) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2022 (Source: China National Influenza Center) Singapore – Acute Respiratory Infection (ARI) Surveillance In week 51 of 2022, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,168 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.4%. Of 693 samples tested for influenza in the past four weeks, the positivity rate in the community was 11.7%. Of the 78 specimens tested positive for influenza in November 2022, 57 were positive for Influenza A(H3N2) (73.0%), 7 were positive for Influenza A(pH1N1) (8.9%) and 14 were positive for Influenza B (18%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2021-2022 Figure 10: Monthly influenza surveillance for ARI in Singapore, 2020-2022 (Source: Singapore Ministry of Health) Influenza Situation Update | 6 Lao PDR During week 51 of 2022, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 69 cases lower than the previous week. There were 48 samples tested for influenza in week 51, 2022. All samples tested positive for influenza, including 5 cases for Influenza B Victoria (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2018 to 2022) (Source: Lao National Center for Laboratory and Epidemiology) Cambodia In week 51 of 2022, Ministry of Health received data from all seven-sentinel sites in Cambodia. The number of ILI cases in Cambodia slightly increased in week 51 of 2022 (130 cases) compared to week 50 of 2022 (127 cases). The influenza positivity rate decreased in week 51 of 2022 (0%) compared to the influenza positivity rate in week 50 (66.7%) (Figure 12). Figure 12: Number of ILI cases from seven sentinel sites and influenza positivity rate by week, 2020-2022, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Influenza Situation Update | 7 Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year to 13 November 2022, there have been 227,359 notifications reported to the National Notifiable Diseases Surveillance System in Australia. Of these, 824 notifications had a diagnosis date in the latest reported fortnight (31 October 2022 - 13 November 2022). This is higher than the number of notifications with a diagnosis date in the previous fortnight (778). The weekly number of notifications of laboratory-confirmed influenza in 2022 has decreased to below the weekly 5 year average since mid- July (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2017 to 2022 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) New Zealand – Influenza like Illness In the four weeks to 25 November 2022, the influenza like illness (ILI) general practitioner consultation rate declined (Figure 14). GP consultation rates remain lower than the historical rate for this time of year. Rates were highest in Counties Manukau, which were higher than observed historically, though showed a decrease throughout the month. Week ending Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2020-2022 (Source: New Zealand Institute of Environmental Science and Research) Influenza Situation Update | 8 Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 50 of 2022, 14 out of 18 PICs reported ILI surveillance data. No reports are available for American Samoa, Guam and Nauru. The following countries reported increased influenza-like illness activity, compared with 2019–2021 trends: Fiji, French Polynesia, Federated States of Micronesia, Samoa, Vanuatu and Wallis and Futuna (Figure 15). Influenza Situation Update | 9 Influenza Situation Update | 10 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sitesreporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2022 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Influenza Situation Update | 11 Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. 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Bi-weekly Influenza Situation Update 18 January 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 2 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported from week 1 to week 2 of 2023 have been Influenza A (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1, 2023to week 51, 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, week 51, 2021 to week 51, 2022 (Source: WHO FLUNET) Country (most recent week of report) Total number of specimens processed Total number of influenza positive specimens Australia (2 of 2023) 23 0 Cambodia - 6 China (1 of 2023) 9136 17 Fiji - - Japan - - Lao People’s Democratic Republic (1 of 2023) 75 0 Malaysia (1 of 2023) 808 270 Mongolia - - New Caledonia - - New Zealand - - Papua New Guinea - - Philippines (1 of 2023) 16 0 Republic of Korea - - Singapore (1 of 2023) 125 21 Viet Nam - - Influenza Situation Update| 2 Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza acitivity is similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 1 of 2023, sentinel hospitals in the northern provinces reported an ILI% of 2.8%, a decrease from the previous week of 5.3% and lower than the same weeks in 2019 to 2021 (5.9%, 2.5% and 4.1%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in Northern China, 2019-2023 (Source: China National Influenza Center) Influenza Situation Update| 3 Mongolia During week 52 of 2022, the ILI activity in Mongolia increased to 75 ILI cases per 10,000 population. This is higher than the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2022 (Source: Mongolia National Influenza Center) Republic of Korea In week 1 of 2023, the overall weekly ILI rate was 52.5 ILI cases per 1,000 outpatient visits, which is lower than the previous week (60.7 per 1,000 outpatients) (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2017-2023 (Source: Korean Centres for Disease Control and Prevention) ILI (p er 1 ,0 00 O ut pa tie nt C on su lta tio ns ) Influenza Situation Update| 4 Sentinel influenza surveillance Japan In week 52 of 2022, the number of cases reported weekly by sentinel hospital sites remained very low in Japan. The number of cases in 2022 has been consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2012-2022 (Source: Japan National Institute of Infectious Diseases) Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed that the overall seasonal influenza activity in Hong Kong remained low. In week 1, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 0.5 ILI cases per 1,000 consultations, which was higher than 0.3 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 18.0 ILI cases per 1,000 consultations, which was higher than 9.9 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2022 Figure 7: ILI consultation rates at sentinel private doctors, Hong Kong SAR 2018-2022 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) Influenza Situation Update| 5 China (South) - ILI Surveillance During week 1 of 2023, the percentage of visits for ILI at national sentinel hospitals in Southern China was 3.6 %, lower than the last week (8.4%) and higher than the same week of 2020 (3.4% ) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2022 (Source: China National Influenza Center) Singapore – Acute Respiratory Infection (ARI) Surveillance In week 52 of 2022, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,336 (over 4.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.4%. Of 578 samples tested for influenza in the past four weeks, the positivity rate in the community was 14.0 %. Of the 86 specimens tested positive for influenza in December 2022, 46 were positive for Influenza A(H3N2) (53.0%), 12 were positive for Influenza A(H1N1)pdm09 (14.0%) and 28 were positive for Influenza B (33.0%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2021-2022 Figure 10: Monthly influenza surveillance for ARI in Singapore, 2020-2022 (Source: Singapore Ministry of Health) Influenza Situation Update| 6 Lao PDR During week 2 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 1 cases more than the previous week. There were 41 samples tested for influenza in week 1, 2023. All samples tested negative for influenza (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2018 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Cambodia In week 51 of 2022 Ministry of Health received data from all seven-sentinel sites in Cambodia. The number of ILI cases in Cambodia slightly increased in week 52 of 2022 (135 cases) compared to week 1 of 2023 (163cases). The influenza positivity rate rincreased slightly in week 1 of 2023 (35.29%) compared to the influenza positivity rate in week 52 of 2022 (0%) (Figure 12). Figure 12: Number of ILI cases from seven sentinel sites and influenza positivity rate by week, 2020-2022, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Influenza Situation Update| 7 Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year to 13 November 2022, there have been 227,359 notifications reported to the National Notifiable Diseases Surveillance System in Australia. Of these, 824 notifications had a diagnosis date in the latest reported fortnight (31 October 2022 - 13 November 2022). This is higher than the number of notifications with a diagnosis date in the previous fortnight (778). The weekly number of notifications of laboratory-confirmed influenza in 2022 has decreased to below the weekly 5 year average since mid- July (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2017 to 2022 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) New Zealand – Influenza like Illness In the four weeks to 25 November 2022, the influenza like illness (ILI) general practitioner consultation rate declined (Figure 14). GP consultation rates remain lower than the historical rate for this time of year. Rates were highest in Counties Manukau, which were higher than observed historically, though showed a decrease throughout the month. Week ending Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2020-2022 (Source: New Zealand Institute of Environmental Science and Research) Influenza Situation Update| 8 Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 1 of 2023, 13 out of 18 PICs reported ILI surveillance data. No reports are available for American Samoa, Guam and Nauru. The following countries reported increased influenza-like illness activity, compared with 2019–2021 trends: Fiji (predominantly Influenza A(H1N1)pdm09) , French Polynesia (currently Influenza A outbreak), Republic of Marshall Islands, Samoa and Wallis and Futuna. The following countries have not reported updated data for week 1, 2023: Vanuatu, Federated states of Micronesia, Solomon islands, Tuvalu and French Polynesia (Figure 15). Influenza Situation Update| 9 Influenza Situation Update| 10 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sitesreporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2022 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. 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Bi-weekly Influenza Situation Update 01 February 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 3 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported from week 1 to week 3 of 2023 have been Influenza B (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1, 2023 to week 3 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, week 51, 2021 to week 51, 2022 (Source: WHO FLUNET) Country (most recent week of report) Total number of specimens processed Total number of influenza positive specimens Australia (2 of 2023) 23 0 Cambodia (1 of 2023) 89 6 China (3 of 2023) 34801 53 Fiji (2 of 2023) 228 101 Japan (2 of 2023) - 79 Lao People’s Democratic Republic (3 of 2023) 270 4 Malaysia (3 of 2023) 2530 800 Mongolia 226 57 New Caledonia - - New Zealand - - Papua New Guinea - - Philippines (1 of 2023) 16 0 Republic of Korea (2 of 2023) 568 154 Singapore (3 of 2023) 421 60 Viet Nam - - Influenza Situation Update| 2 Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza acitivity is similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 3 of 2023, sentinel hospitals in the northern provinces reported an ILI% of 2.1%, higher than the previous week of 1.9% and lower than the same weeks in 2019 to 2021 (4.5%, 2.6% and 3.1%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in Northern China, 2019-2023 (Source: China National Influenza Center) Mongolia During week 2 of 2023, the ILI activity in Mongolia decreased to 63 ILI cases per 10,000 population. This is higher than the upper tolerance limit (Figure 3). Influenza Situation Update| 3 Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Republic of Korea In week 3 of 2023, the overall weekly ILI rate was 82.3 ILI cases per 1,000 outpatient visits, which is lower than the previous week (40.2 per 1,000 outpatients) (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2017-2023 (Source: Korean Centres for Disease Control and Prevention) ILI (p er 1 ,0 00 O ut pa tie nt C on su lta tio ns ) Influenza Situation Update| 4 Sentinel influenza surveillance Japan In week 2 of 2023, the number of cases reported weekly by sentinel hospital sites remained very low in Japan. The number of cases in 2022 was consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2012-2023 (Source: Japan National Institute of Infectious Diseases) Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed that the overall seasonal influenza activity in Hong Kong remained low. In week 3, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 0.3 ILI cases per 1,000 consultations, which was higher than 0.9 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 15.4 ILI cases per 1,000 consultations, which was lower than 24.4 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private doctors, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) Influenza Situation Update| 5 China (South) - ILI Surveillance During week 3 of 2023, the percentage of visits for ILI at national sentinel hospitals in Southern China was 1.9 %, lower than the last week (2.2%) and higher than the same week of 2019-2021 (5.1%, 3.4% and 3.5 ) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2022 (Source: China National Influenza Center) Singapore – Acute Respiratory Infection (ARI) Surveillance In week 52 of 2022, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,336 (over 4.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.4%. Of 578 samples tested for influenza in the past four weeks, the positivity rate in the community was 14.0 %. Of the 86 specimens tested positive for influenza in December 2022, 46 were positive for Influenza A(H3N2) (53.0%), 12 were positive for Influenza A(H1N1) pdm09 (14.0%) and 28 were positive for Influenza B (33.0%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2021-2022 Figure 10: Monthly influenza surveillance for ARI in Singapore, 2020-2022 (Source: Singapore Ministry of Health) Influenza Situation Update| 6 Lao PDR During week 3 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 6 cases higher than the previous week. There were 63 samples tested for influenza in week 3, 2023. All samples tested positive for influenza Flu B Vic (n=3) (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2018 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Cambodia In week 2 of 2023 Ministry of Health received data from all 12 sentinel sites in Cambodia. The number of ILI cases in Cambodia slightly decreased in week 1 of 2023 (163 cases) compared to week 2 of 2023 (152cases). The influenza positivity rate decreased slightly in week 2 of 2023 (8.3%) compared to the influenza positivity rate in week 1 of 2023 (35.3%) (Figure 12). Figure 12: Number of ILI cases from seven sentinel sites and influenza positivity rate by week, 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Influenza Situation Update| 7 Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year to 13 November 2022, there have been 227,359 notifications reported to the National Notifiable Diseases Surveillance System in Australia. Of these, 824 notifications had a diagnosis date in the latest reported fortnight (31 October 2022 - 13 November 2022). This is higher than the number of notifications with a diagnosis date in the previous fortnight (778). The weekly number of notifications of laboratory-confirmed influenza in 2022 has decreased to below the weekly 5 year average since mid- July (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2017 to 2022 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) New Zealand – Influenza like Illness In the four weeks to 25 November 2022, the influenza like illness (ILI) general practitioner consultation rate declined (Figure 14). GP consultation rates remain lower than the historical rate for this time of year. Rates were highest in Counties Manukau, which were higher than observed historically, though showed a decrease throughout the month. Week ending Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2020-2022 (Source: New Zealand Institute of Environmental Science and Research) Influenza Situation Update| 8 Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 3 of 2023, 15 out of 18 PICs reported ILI surveillance data. No reports are available for American Samoa, Guam and Nauru. The following countries reported increased influenza-like illness activity, compared with 2019–2021 trends: Fiji (predominantly Influenza A(H1N1) pdm09), Federated States of Micronesia, French Polynesia (currently Influenza A outbreak), Republic of Marshall Islands, Samoa and Wallis and Futuna. The following countries have not reported updated data for week 3, 2023: Pitcairn Islands, Tokelau and Tuvalu, (Figure 15). Influenza Situation Update| 9 Influenza Situation Update| 10 Influenza Situation Update| 11 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2022 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. 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Influenza Situation Update| 1 Bi-weekly Influenza Situation Update 15 February 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 5 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported from week 1 to week 5 of 2023 have been Influenza B (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1, 2023 to week 5 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, week 5, 2022 to week 5, 2023 (Source: WHO FLUNET ) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. Country (most recent week of report) Total number of specimens processed Total number of influenza positive specimens Australia (5 of 2023) 1,5623 152 Cambodia (2 of 2023) 177 9 China (5 of 2023) 58,283 148 Fiji (2 of 2023) 74 40 Japan (4 of 2023) - 225 Lao People’s Democratic Republic (5 of 2023) 471 12 Malaysia (5 of 2023) 4,132 1,323 Mongolia (1 of 2023) 226 57 New Caledonia - - New Zealand - - Papua New Guinea - - Philippines (1 of 2023) 16 0 Republic of Korea (5 of 2023) 1,182 225 Singapore (5 of 2023) 748 109 Viet Nam - - Influenza Situation Update| 2 Bi-weekly Influenza Situation Update 15 February 2023 The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza acitivity is similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 5 of 2023, sentinel hospitals in the northern provinces reported an ILI% of 1.4%, lower than the previous week of 2% and lower than the same weeks in 2020 to 2022 (8.4%, 2% and 3.5%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in Northern China, 2019-2023 (Source: China National Influenza Center) Mongolia During week 4 of 2023, the ILI activity in Mongolia decreased to 58 ILI cases per 10,000 population. This is higher than the upper tolerance limit (Figure 3). Influenza Situation Update| 3 Bi-weekly Influenza Situation Update 15 February 2023 Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Republic of Korea In week 5 of 2023, the overall weekly ILI rate was 17 ILI cases per 1,000 outpatient visits, which is lower than the previous week (25.6 per 1,000 outpatients) (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2017-2023 (Source: Korean Centres for Disease Control and Prevention) Sentinel influenza surveillance Japan In week 4 of 2023, the number of cases reported weekly by sentinel hospital sites remained very low in Japan. The number of cases in 2022 was consistently low (Figure 5). IL I ( p er 1 ,0 00 O u tp at ie n t C o n su lt at io n s) Influenza Situation Update| 4 Bi-weekly Influenza Situation Update 15 February 2023 Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2012-2023 (Source: Japan National Institute of Infectious Diseases) Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed that the overall seasonal influenza activity in Hong Kong remained low. In week 4, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 1.2 ILI cases per 1,000 consultations, which was higher than 0.3 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 16.9 ILI cases per 1,000 consultations, which was higher than 15.4 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private doctors, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) Influenza Situation Update| 5 Bi-weekly Influenza Situation Update 15 February 2023 China (South) - ILI Surveillance During week 5 of 2023, the percentage of visits for ILI at national sentinel hospitals in Southern China was 1.4 %, lower than the last week (1.9%) and lower than the same week of 2020-2022 (8.2%, 2.5% and 3.9 ) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2022 (Source: China National Influenza Center) Singapore – Acute Respiratory Infection (ARI) Surveillance In week 52 of 2022, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,336 (over 4.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.4%. Of 578 samples tested for influenza in the past four weeks, the positivity rate in the community was 14.0 %. Of the 86 specimens tested positive for influenza in December 2022, 46 were positive for Influenza A(H3N2) (53.0%), 12 were positive for Influenza A(H1N1) pdm09 (14.0%) and 28 were positive for Influenza B (33.0%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2021-2022 Figure 10: Monthly influenza surveillance for ARI in Singapore, 2020-2022 (Source: Singapore Ministry of Health) Influenza Situation Update| 6 Bi-weekly Influenza Situation Update 15 February 2023 Lao PDR During week 5 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 9 cases lower than the previous week. There were 60 samples tested for influenza in week 5, 2023. Influenza Flu B Vic was the dominant type identified (n=6) (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2018 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Cambodia In week 4 of 2023 Ministry of Health received data from all 14 sentinel sites in Cambodia. The number of ILI cases in Cambodia slightly increased in week 4 of 2023 (182 cases) compared to week 3 of 2023 (156cases). The influenza positivity rate increased slightly in week 4 of 2023 (7.1%) compared to the influenza positivity rate in week 3 of 2023 (6.3%) (Figure 12). Figure 12: Number of ILI cases from seven sentinel sites and influenza positivity rate by week, 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Influenza Situation Update| 7 Bi-weekly Influenza Situation Update 15 February 2023 Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year to 13 November 2022, there have been 227,359 notifications reported to the National Notifiable Diseases Surveillance System in Australia. Of these, 824 notifications had a diagnosis date in the latest reported fortnight (31 October 2022 - 13 November 2022). This is higher than the number of notifications with a diagnosis date in the previous fortnight (778). The weekly number of notifications of laboratory-confirmed influenza in 2022 has decreased to below the weekly 5 year average since mid- July (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2017 to 2022 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) New Zealand – Influenza like Illness In the four weeks to 25 November 2022, the influenza like illness (ILI) general practitioner consultation rate declined (Figure 14). GP consultation rates remain lower than the historical rate for this time of year. Rates were highest in Counties Manukau, which were higher than observed historically, though showed a decrease throughout the month. Week ending Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2020-2022 (Source: New Zealand Institute of Environmental Science and Research) Influenza Situation Update| 8 Bi-weekly Influenza Situation Update 15 February 2023 Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 5 of 2023, 16 out of 18 PICs reported ILI surveillance data. No reports are available for American Samoa, Guam and Nauru. The following countries reported increased influenza-like illness activity, compared with 2019–2021 trends: Fiji (predominantly Influenza A(H1N1) pdm09), Federated States of Micronesia, French Polynesia ((Influenza A/H3 predominant), Republic of Marshall Islands, Samoa and Wallis and Futuna. The following countries have not reported updated data for week 5, 2023: French Polynesia and Tuvalu, (Figure 15). Influenza Situation Update| 9 Bi-weekly Influenza Situation Update 15 February 2023 Influenza Situation Update| 10 Bi-weekly Influenza Situation Update 15 February 2023 Influenza Situation Update| 11 Bi-weekly Influenza Situation Update 15 February 2023 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2022 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. 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Bi-weekly Influenza Situation Update 01 March 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 7 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 7 of 2023 have been Influenza A(H1N1)pdm09 (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1, 2023 to week 7 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, week 7, 2022 to week 7, 2023 (Source: WHO FLUNET ) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. Country (most recent week of report) Total number of specimens processed Total number of influenza positive specimens Australia (7 of 2023) 21,509 202 Cambodia (6 of 2023) 540 14 China (7 of 2023) 100,381 2,572 Fiji (3 of 2023) 74 40 Japan (6 of 2023) - 397 Lao People’s Democratic Republic (7 of 2023) 723 20 Malaysia (7 of 2023) 5,887 1,795 Mongolia (6 of 2023) 3,250 982 New Caledonia - - New Zealand - - Papua New Guinea - - Philippines (6 of 2023) 394 16 Republic of Korea (5 of 2023) 1,182 225 Singapore (7 of 2023) 1,179 200 Viet Nam - - Influenza Situation Update | 2 The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza acitivity is similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 7 of 2023, sentinel hospitals in the northern provinces reported an ILI% of 1.9%, higher than the previous week of 1.4% and lower than the same weeks in 2020 to 2022 (5.4%, 2.0% and 1.9%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in Northern China, 2019-2023 (Source: China National Influenza Center) Influenza Situation Update | 3 Mongolia During week 6 of 2023, the ILI activity in Mongolia decreased to 71 ILI cases per 10,000 population. This is higher than the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Republic of Korea In week 7 of 2023, the overall weekly ILI rate was 15 ILI cases per 1,000 outpatient visits, which is lower than the previous week (15.2 per 1,000 outpatients) (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korean Centres for Disease Control and Prevention) ILI (p er 1 ,0 00 O ut pa tie nt C on su lta tio ns ) Influenza Situation Update | 4 Sentinel influenza surveillance Japan In week 6 of 2023, the number of cases reported weekly by sentinel hospital sites remained very low in Japan. The number of cases in 2022 was consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed that the overall seasonal influenza activity in Hong Kong remained low. In week 7, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 1.2 ILI cases per 1,000 consultations, which was higher than 0.7 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 30.6 ILI cases per 1,000 consultations, which was lower than 32.4 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private doctors, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) Influenza Situation Update | 5 China (South) - ILI Surveillance During week 7 of 2023, the percentage of visits for ILI at national sentinel hospitals in Southern China was 1.8 %,higher than the last week (1.4%) and lower than the same week of 2020-2022 (4.8%, 2.7% and 2.6% ) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2022 (Source: China National Influenza Center) Singapore – Acute Respiratory Infection (ARI) Surveillance In week 7 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,590 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.5%. Of 758 samples tested for influenza in the past four weeks, the positivity rate in the community was 18.5 %. Of the 96 specimens tested positive for influenza in January 2023, 37 were positive for Influenza A(H3N2) (38.5%), 13 were positive for Influenza A(H1N1) pdm09 (13.5%) and 46 were positive for Influenza B (48%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 (Source: Singapore Ministry of Health) Influenza Situation Update | 6 Lao PDR During week 7of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 15 cases higher than the previous week. There were125 samples tested for influenza in week 7, 2023. Influenza Flu B Vic was the dominant type identified (n=5) (Figure 11) Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Cambodia In week 6 of 2023 Ministry of Health received data from all 12 sentinel sites in Cambodia. The number of ILI cases in Cambodia slightly increased in week 6 of 2023 (175 cases) compared to week 5 of 2023 (173 cases). The influenza positivity rate increased slightly in week 6 of 2023 (6.7%) compared to the influenza positivity rate in week 5 of 2023 (0%) (Figure 12). Figure 12: Number of ILI cases from seven sentinel sites and influenza positivity rate by week, 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Influenza Situation Update | 7 Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year to 13 November 2022, there have been 227,359 notifications reported to the National Notifiable Diseases Surveillance System in Australia. Of these, 824 notifications had a diagnosis date in the latest reported fortnight (31 October 2022 - 13 November 2022). This is higher than the number of notifications with a diagnosis date in the previous fortnight (778). The weekly number of notifications of laboratory-confirmed influenza in 2022 has decreased to below the weekly 5 year average since mid- July (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2017 to 2022 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) New Zealand – Influenza like Illness In the four weeks to 25 November 2022, the influenza like illness (ILI) general practitioner consultation rate declined (Figure 14). GP consultation rates remain lower than the historical rate for this time of year. Rates were highest in Counties Manukau, which were higher than observed historically, though showed a decrease throughout the month. Week ending Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2020-2022 (Source: New Zealand Institute of Environmental Science and Research) Influenza Situation Update | 8 Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 7 of 2023, 18 out of 21 PICs reported ILI surveillance data. No reports are available for American Samoa, Guam and Nauru. The following countries reported increased influenza-like illness activity, compared with the same weeks in 2022: Cook Islands, Fiji, Federated States of Micronesia, Kiribati, Republic of Marshall Islands,Commonwealth of the Northern Mariana islands, Samoa, Tonga, Vanuatu and Wallis and Futuna. The following countries have not reported updated data for week 7, 2023: French Polynesia and Tuvalu, (Figure 15). Influenza Situation Update | 9 Influenza Situation Update | 10 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. 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Influenza Situation Update| 1 Bi-weekly Influenza Situation Update 15 March 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 8 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 8 of 2023 have been Influenza A(H1N1)pdm09 (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1, 2023 to week 8 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, Week 8 2022 to week 8, 2023 (Source: WHO FLUNET ) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an Country (most recent week of report) Total number of specimens processed Total number of influenza positive specimens Australia (7 of 2023) 14,901 192 Cambodia (6 of 2023) - 5 China (7 of 2023) 78,838 21,313 Fiji (3 of 2023) - - Japan (6 of 2023) - 154 Lao People’s Democratic Republic (7 of 2023) 449 11 Malaysia (7 of 2023) 3,595 855 Mongolia (6 of 2023) 1,454 3,298 New Caledonia - - New Zealand - - Papua New Guinea - - Philippines (6 of 2023) 133 14 Republic of Korea (5 of 2023) 1,048 73 Singapore (7 of 2023) 959 223 Viet Nam - - Influenza Situation Update| 2 Bi-weekly Influenza Situation Update 15 March 2023 acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 8 of 2023, sentinel hospitals in the northern provinces reported an ILI% of 4.4%, higher than the previous week of 1.9% and lower than the same week in 2020 (4.4%) and higher than the same week of 2021-2022 (1.6%, 1.9%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in Northern China, 2019-2023 (Source: China National Influenza Center) Mongolia During week 8 of 2023, the ILI activity in Mongolia decreased to 57 ILI cases per 10,000 population. This is higher than the upper tolerance limit (Figure 3). Influenza Situation Update| 3 Bi-weekly Influenza Situation Update 15 March 2023 Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Republic of Korea In week 9 of 2023, the overall weekly ILI rate was11.9 ILI cases per 1,000 outpatient visits, which is lower than the previous week (15 per 1,000 outpatients) (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korean Centres for Disease Control and Prevention) IL I ( p er 1 ,0 00 O u tp at ie n t C o n su lt at io n s) Influenza Situation Update| 4 Bi-weekly Influenza Situation Update 15 March 2023 Sentinel influenza surveillance Japan In week 10 of 2023, the number of cases reported weekly by sentinel hospital sites remained very low in Japan. The number of cases in 2022 was consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed that the overall seasonal influenza activity in Hong Kong remained low. In week 9, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 1.3 ILI cases per 1,000 consultations, which was higher than the 0.8 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 20.9 ILI cases per 1,000 consultations, which was lower than the 25.7 recorded in the previous week (Figure 7). Influenza Situation Update| 5 Bi-weekly Influenza Situation Update 15 March 2023 Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private doctors, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) China (South) - ILI Surveillance During week 8 of 2023, the percentage of visits for ILI at national sentinel hospitals in Southern China was 3.9 %, higher than the last week (1.8%) and lower than the same week of 2020-2022 (3.7%, 2.2% and 3.1% ) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2022 (Source: China National Influenza Center) Singapore – Acute Respiratory Infection (ARI) Surveillance In week 9 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,535 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.5%. Of 959 samples tested for influenza in the past four weeks, the positivity rate in the community was 23.4%. Of the 198 specimens that tested positive for influenza in January 2023, 127 were positive for Influenza A(H3N2) (64%), 23 were positive for Influenza A(H1N1) pdm09 (12%) and 48 were positive for Influenza B (24%) (Figure 10). Influenza Situation Update| 6 Bi-weekly Influenza Situation Update 15 March 2023 Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 (Source: Singapore Ministry of Health) Lao PDR During week 8 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 10 cases higher than the previous week. There were 128 samples tested for influenza in week 8, 2023. Influenza Flu B Vic was identified (n=1) (Figure 11) Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Cambodia In week 9 of 2023, the Ministry of Health received data from all seven sentinel sites in Cambodia. The number of ILI cases in Cambodia slightly increased in week 9 of 2023 (166 cases) compared to week 8 of 2023 (152 cases). The influenza positivity rate increased slightly in week 9 of 2023 (16.67%) compared to the influenza positivity rate in week 6 of 2023 (6.7) (Figure 12). Influenza Situation Update| 7 Bi-weekly Influenza Situation Update 15 March 2023 Figure 12: Number of ILI cases from seven sentinel sites and influenza positivity rate by week, 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year to 13 November 2022, there have been 227,359 notifications reported to the National Notifiable Diseases Surveillance System in Australia. Of these, 824 notifications had a diagnosis date in the latest reported fortnight (31 October 2022 - 13 November 2022). This is higher than the number of notifications with a diagnosis date in the previous fortnight (778). The weekly number of notifications of laboratory-confirmed influenza in 2022 has decreased to below the weekly 5-year average since mid- July (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2017 to 2022 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) New Zealand – Influenza like Illness In the four weeks to 25 November 2022, the influenza like illness (ILI) general practitioner consultation rate declined (Figure 14). GP consultation rates remain lower than the historical rate for this time of Influenza Situation Update| 8 Bi-weekly Influenza Situation Update 15 March 2023 year. Rates were highest in Counties Manukau, which were higher than observed historically, though showed a decrease throughout the month. Week ending Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2020-2022 (Source: New Zealand Institute of Environmental Science and Research) Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 9 of 2023, 18 out of 21 PICs reported ILI surveillance data. No reports are available for American Samoa, Guam, and Nauru. The following countries reported increased influenza-like illness activity, compared with the same weeks in 2022: Cook Islands, Federated States of Micronesia, Kiribati, Republic of Marshall Islands, Commonwealth of the Northern Mariana Islands, Samoa, Tonga (Influenza B outbreak is ongoing), Vanuatu and Wallis and Futuna. (Figure 15). Influenza Situation Update| 9 Bi-weekly Influenza Situation Update 15 March 2023 Influenza Situation Update| 10 Bi-weekly Influenza Situation Update 15 March 2023 Influenza Situation Update| 11 Bi-weekly Influenza Situation Update 15 March 2023 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. 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Influenza Situation Update| 1 Bi-weekly Influenza Situation Update 29 March 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 11 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 11 of 2023 have been Influenza A(H1N1)pdm09 (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1, 2023 to week 11 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, Week 11 2022 to week 11, 2023 (Source: WHO FLUNET ) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population Country (most recent week of report) Total number of specimens processed Total number of influenza positive specimens Australia (11 of 2023) 37,053 446 Cambodia (9 of 2023) 827 25 China (11 of 2023) 209,569 51,332 Fiji (10 of 2023) 855 221 Japan (11 of 2023) - 1,144 Lao People’s Democratic Republic (11 of 2023) 1,098 31 Malaysia (11 of 2023) 93,98 2,470 Mongolia (10 of 2023) 5,214 1,349 New Caledonia - - New Zealand - - Papua New Guinea - - Philippines (11 of 2023) 765 56 Republic of Korea (11 of 2023) 3,194 332 Singapore (11 of 2023) 2,398 534 Viet Nam - - Influenza Situation Update| 2 Bi-weekly Influenza Situation Update 29 March 2023 groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 11 of 2023, sentinel hospitals in the northern provinces reported an ILI% of 7.7%, lower than the last week of 8.7% and higher than the same week of week of 2020-2022 (2.5%, 1.9% and 2.4%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in Northern China, 2019-2023 (Source: China National Influenza Center) Mongolia During week 11 of 2023, the ILI activity in Mongolia decreased to 53 ILI cases per 10,000 population. This is higher than the upper tolerance limit (Figure 3). Influenza Situation Update| 3 Bi-weekly Influenza Situation Update 29 March 2023 Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Republic of Korea In week 11 of 2023, the overall weekly ILI rate was 11.7 ILI cases per 1,000 outpatient visits, which was equal 11.7% recorded in the previous week. (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korean Centres for Disease Control and Prevention) Sentinel influenza surveillance Japan In week 10 of 2023, the number of cases reported weekly by sentinel hospital sites remained very low in Japan. The number of cases in 2022 was consistently low (Figure 5). IL I ( p er 1 ,0 00 O u tp at ie n t C o n su lt at io n s) Influenza Situation Update| 4 Bi-weekly Influenza Situation Update 29 March 2023 Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed that the overall seasonal influenza activity in Hong Kong remained low. In week 11, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 1.3 ILI cases per 1,000 consultations, which was lower than the 1.5 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 30.7 ILI cases per 1,000 consultations, which was lower than the 31.1 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private doctors, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) Influenza Situation Update| 5 Bi-weekly Influenza Situation Update 29 March 2023 China (South) - ILI Surveillance During week 11 of 2023, the percentage of visits for ILI at national sentinel hospitals in Southern China was 9.8 %, lower than the last week (10.0%) and higher than the same week of 2020-2022 (2.7%, 2.8% and 4.3% ) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2022 (Source: China National Influenza Center) Singapore – Acute Respiratory Infection (ARI) Surveillance In week 11 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,592 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.4%. Of 1,219 samples tested for influenza in the past four weeks, the positivity rate in the community was 27.5%. Of the 198 specimens that tested positive for influenza in February 2023, 127 were positive for Influenza A(H3N2) (64%), 23 were positive for Influenza A(H1N1) pdm09 (12%) and 48 were positive for Influenza B (24%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 Influenza Situation Update| 6 Bi-weekly Influenza Situation Update 29 March 2023 (Source: Singapore Ministry of Health) Lao PDR During week 11 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 92 cases higher than the previous week. There were 100 samples tested for influenza in week 11, 2023. Influenza A/pdmH1N1 was identified (n=5) and Flu A/H3 (n=1) (Figure 11) Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Cambodia In week 11 of 2023, the Ministry of Health received data from all seven sentinel sites in Cambodia. The number of ILI cases in Cambodia slightly increased in week 11 of 2023 (176 cases) compared to week 10 of 2023 (144 cases). There was no positive influenza case in week 11. (Figure 12). Figure 12: Number of ILI cases from seven sentinel sites and influenza positivity rate by week, 2020-2023, Cambodia Influenza Situation Update| 7 Bi-weekly Influenza Situation Update 29 March 2023 (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year to 13 November 2022, there have been 227,359 notifications reported to the National Notifiable Diseases Surveillance System in Australia. Of these, 824 notifications had a diagnosis date in the latest reported fortnight (31 October 2022 - 13 November 2022). This is higher than the number of notifications with a diagnosis date in the previous fortnight (778). The weekly number of notifications of laboratory-confirmed influenza in 2022 has decreased to below the weekly 5-year average since mid- July (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2017 to 2022 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) New Zealand – Influenza like Illness In the four weeks to 25 November 2022, the influenza like illness (ILI) general practitioner consultation rate declined (Figure 14). GP consultation rates remain lower than the historical rate for this time of year. Rates were highest in Counties Manukau, which were higher than observed historically, though showed a decrease throughout the month. Week ending Influenza Situation Update| 8 Bi-weekly Influenza Situation Update 29 March 2023 Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2020-2022 (Source: New Zealand Institute of Environmental Science and Research) Pacific Island Countries and Areas (PICs) - ILI Surveillance In week9 of 2023, 18 out of 21 PICs reported ILI surveillance data. No reports are available for American Samoa, Guam, and Nauru. The following countries reported increased influenza-like illness activity, compared with the same weeks in 2022: Cook Islands, Federated States of Micronesia, Kiribati, Republic of Marshall Islands, Commonwealth of the Northern Mariana Islands, Samoa, Tonga (Influenza B outbreak is ongoing), Vanuatu and Wallis and Futuna. (Figure 15). Influenza Situation Update| 9 Bi-weekly Influenza Situation Update 29 March 2023 Influenza Situation Update| 10 Bi-weekly Influenza Situation Update 29 March 2023 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Influenza Situation Update| 11 Bi-weekly Influenza Situation Update 29 March 2023 Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. 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Bi-weekly Influenza Situation Update 12 April 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 13 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 13 of 2023 have been Influenza A(H1N1)pdm09 (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1, 2023 to week 13 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, Week 13 2022 to week 13, 2023 (Source: WHO FLUNET ) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. Country (most recent week of report) Total number of specimens processed Total number of influenza-positive specimens Australia (13 of 2023) 40,532 501 Cambodia (13 of 2023) 827 25 China (13 of 2023) 241,226 78,812 Fiji (10 of 2023) 855 221 Japan (13 of 2023) - 1,440 Lao People’s Democratic Republic (12 of 2023) 1,367 65 Malaysia (13 of 2023) 11,121 2,745 Mongolia (12 of 2023) 6,881 1,485 New Caledonia - - New Zealand - - Papua New Guinea - - Philippines (13 of 2023) 964 70 Republic of Korea (13 of 2023) 3,559 351 Singapore (13 of 2023) 3,126 714 Viet Nam - - Influenza Situation Update| 2 The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 13 of 2023, sentinel hospitals in the northern provinces reported an ILI% of 4.4%, lower than the last week of 5.8% and higher than the same week of 2020-2022 (2.3%, 2.2%, and 2.0%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in Northern China, 2019-2023 Source: China National Influenza Center) Mongolia During week 12 of 2023, the ILI activity in Mongolia decreased to 32 ILI cases per 10,000 population. This is below the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Influenza Situation Update| 3 Republic of Korea In week 13 of 2023, the overall weekly ILI rate was 14.5 ILI cases per 1,000 outpatient visits, which was higher 13.2% recorded in the previous week. (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korea Disease Control and Prevention Agency) Sentinel influenza surveillance Japan In week 13 of 2023, the number of cases reported weekly by sentinel hospital sites remained low in Japan. The number of cases in 2023 was consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 Source: Japan National Institute of Infectious Diseases) IL I ( p er 1 ,0 00 O u tp at ie n t C o n su lt at io n s) Influenza Situation Update| 4 Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed that the overall seasonal influenza activity in Hong Kong remained low. In week 13, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 1.7 ILI cases per 1,000 consultations, which was lower than the 1.5 recorded in the previous week (Figure 2.1 left). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 42.0 ILI cases per 1,000 consultations, which was lower than the 28.5 recorded in the previous week (Figure 2.1 right). Figure 2.1 Left: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020- 2023 Figure 2.1 Right: ILI consultation rates at sentinel private doctors, Hong Kong SAR 2019-2023 Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) China (South) - ILI Surveillance During week 13 of 2023, the percentage of visits for ILI at national sentinel hospitals in Southern China was 10 %, lower than the last week (10.1%) and higher than the same week of 2020-2022 (2.5%, 3.0%, and 3.5% ) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2022 Source: China National Influenza Center) Influenza Situation Update| 5 Singapore – Acute Respiratory Infection (ARI) Surveillance In week 13 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 2826 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.9%. Of 1,419 samples tested for influenza in the past four weeks, the positivity rate in the community was 26.9%. Of the 421 specimens that tested positive for influenza in March 2023, 258 were positive for Influenza A(H3N2) (61.3%), 94 were positive for Influenza A(H1N1) pdm09 (22.3%) and 68 were positive for Influenza B (16.2%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 Source: Singapore Ministry of Health Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 Source: Singapore Ministry of Health Lao PDR During week 12 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 98 cases higher than the previous week. There were 126 samples tested for influenza in week 12, 2023. Influenza A/pdmH1N1 was identified (n=10) and Flu B Vic (n=5) (Figure 11) Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Influenza Situation Update| 6 Cambodia In week 13 of 2023, the Ministry of Health received data from all seven sentinel sites in Cambodia. The number of ILI cases in Cambodia slightly increased in week 12 of 2023 (124 cases) compared to week 13 of 2023 (130 cases). The positivity rate was 7.14% for this week. (Figure 12). Figure 12: Number of ILI cases from seven sentinel sites and influenza positivity rate by the week, of 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year to 13 November 2022, there have been 227,359 notifications reported to the National Notifiable Diseases Surveillance System in Australia. Of these, 824 notifications had a diagnosis date in the latest reported fortnight (31 October 2022 - 13 November 2022). This is higher than the number of notifications with a diagnosis date in the previous fortnight (778). The weekly number of notifications of laboratory-confirmed influenza in 2022 has decreased to below the weekly 5-year average since mid- July (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2017 to 2022 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) Influenza Situation Update| 7 New Zealand – Influenza like Illness In the four weeks to 25 November 2022, the influenza like illness (ILI) general practitioner consultation rate declined (Figure 14). GP consultation rates remain lower than the historical rate for this time of year. Rates were highest in Counties Manukau, which were higher than observed historically, though showed a decrease throughout the month. Week ending Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2020-2022 (Source: New Zealand Institute of Environmental Science and Research) Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 13 of 2023, 18 out of 21 PICs reported ILI surveillance data. No reports are available for American Samoa, Guam, and Nauru. The following countries reported increased influenza-like illness activity, compared with the same weeks in 2022: Cook Islands, Federated States of Micronesia, Kiribati, Republic of Marshall Islands, Commonwealth of the Northern Mariana Islands, Samoa, Tonga (Influenza B outbreak is ongoing), Vanuatu and Wallis and Futuna. (Figure 15). Influenza Situation Update| 8 Influenza Situation Update| 9 Influenza Situation Update| 10 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Influenza Situation Update| 11 Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. 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Influenza Situation Update| 1 Bi-weekly Influenza Situation Update 26 April 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 15 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 15 of 2023 have been Influenza A(H1N1)pdm09 (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1, 2023 to week 15, 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, Week 15, 2022 to week 15, 2023 (Source: WHO FLUNET ) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. Country (most recent week of report) Total number of specimens processed Total number of influenza-positive specimens Australia (15 of 2023) 48,057 670 Cambodia (09 of 2023) 827 25 China (15 of 2023) 312,993 97,674 Fiji (10 of 2023) 855 221 Japan (14 of 2023) - 1,674 Lao People’s Democratic Republic (15 of 2023) 1,620 114 Malaysia (14 of 2023) 12,008 2,862 Mongolia (13 of 2023) 6,881 1,485 New Caledonia - - New Zealand - - Papua New Guinea - - Philippines (14 of 2023) 1,130 74 Republic of Korea (15 of 2023) 4,269 386 Singapore (15 of 2023) 3,797 872 Viet Nam - - Influenza Situation Update| 2 Bi-weekly Influenza Situation Update 26 April 2023 The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 15 of 2023, sentinel hospitals in the northern provinces reported an ILI% of 2.9%, lower than the last week of 3.2% and higher than the same week of 2020-2022 (1.9%, 2.2%, and 1.7%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in Northern China, 2019-2023 (Source: China National Influenza Center) Mongolia During week 15 of 2023, the ILI activity in Mongolia increased to 44 ILI cases per 10,000 population. This is above the upper tolerance limit (Figure 3). Influenza Situation Update| 3 Bi-weekly Influenza Situation Update 26 April 2023 Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Republic of Korea In week 15 of 2023, the overall weekly ILI rate was 18.5% per 1,000 outpatient visits, which was higher 15.2% recorded in the previous week (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korea Disease Control and Prevention Agency) Sentinel influenza surveillance Japan In week 15 of 2023, the number of cases reported weekly by sentinel hospital sites remained low in Japan. The number of cases in 2023 was consistently low (Figure 5). IL I ( p er 1 ,0 0 0 O u tp at ie n t C o n su lt at io n s) Influenza Situation Update| 4 Bi-weekly Influenza Situation Update 26 April 2023 Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed that the overall seasonal influenza activity in Hong Kong remained low. In week 15, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 3.0 ILI cases per 1,000 consultations, which was higher than the 1.4 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 48.5 ILI cases per 1,000 consultations, which was higher than the 31.0 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private doctors, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) Influenza Situation Update| 5 Bi-weekly Influenza Situation Update 26 April 2023 China (South) - ILI Surveillance During week 15 of 2023, the percentage of visits for ILI at national sentinel hospitals in Southern China was 7.1 %, lower than the last week (8.9%) and higher than the same week of 2020-2022 (2.3%, 3.1%, and 3.0% ) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2023 (Source: China National Influenza Center) Singapore – Acute Respiratory Infection (ARI) Surveillance In week 15 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 3115 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.4%. Of 1,399 samples tested for influenza in the past four weeks, the positivity rate in the community was 24.2%. Of the 421 specimens that tested positive for influenza in March 2023, 258 were positive for Influenza A(H3N2) (61.3%), 94 were positive for Influenza A(H1N1) pdm09 (22.3%), 1 was positive for Influenza A(LVT) (0.2%), and 68 were positive for Influenza B (16.2%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 (Source: Singapore Ministry of Health) Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 (Source: Singapore Ministry of Health) Influenza Situation Update| 6 Bi-weekly Influenza Situation Update 26 April 2023 Lao PDR During week 12 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 98 cases higher than the previous week. There were 126 samples tested for influenza in week 12, 2023. Influenza A/pdmH1N1 was identified (n=10) and Flu B Vic (n=5) (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Cambodia In week 15 of 2023, the Ministry of Health received data from all seven sentinel sites in Cambodia. The number of ILI cases in Cambodia slightly decreased in week 15 (97 cases) of 2023 compared to week 14 (128 cases) . There was no positive case this week (Figure 12). Figure 12: Number of ILI cases from seven sentinel sites and influenza positivity rate by the week, of 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Influenza Situation Update| 7 Bi-weekly Influenza Situation Update 26 April 2023 Australia – Laboratory-confirmed influenza In the year to 16 April 2023, there have been 25,870 notifications of laboratory-confirmed influenza were reported to the National Notifiable Diseases Surveillance System in Australia. There were 6,786 laboratory-confirmed influenza notifications with a diagnosis date this fortnight (3 April 2023 to 16 April 2023), compared to 5,710 notifications in the previous fortnight. From March 2023 the number of notifications of laboratory-confirmed influenza has gradually increased. The number of notifications year-to-date is higher than the 5-year average, but lower than observed in the same period in 2019 (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2016 to 2023 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) New Zealand – Influenza like Illness In the week ending of 16 April 2023, the influenza like illness (ILI) general practitioner consultation(Figure 14) rates remain at a similar level to the historical rate for this time of year. As of 16 April, national influenza-like illness (ILI) activity remains low. However, in Counties Manukau and MidCentral ILI activity has been increasing and is at higher than expected level for this year. Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2015-2023 (Source: New Zealand Institute of Environmental Science and Research) Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 15 of 2023, 18 out of 21 PICs reported ILI surveillance data. No reports are available for American Samoa, Guam, and Nauru. The following countries reported increased influenza-like illness activity: Federated States of Micronesia, Niue, Kiribati, and Samoa (Figure 15). Influenza Situation Update| 8 Bi-weekly Influenza Situation Update 26 April 2023 Influenza Situation Update| 9 Bi-weekly Influenza Situation Update 26 April 2023 Influenza Situation Update| 10 Bi-weekly Influenza Situation Update 26 April 2023 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Influenza Situation Update| 11 Bi-weekly Influenza Situation Update 26 April 2023 Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. 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Bi-weekly Influenza Situation Update 10 May 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 17 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 17 of 2023 have been Influenza A(H1N1)pdm09 (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1, 2023 to week 17, 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, Week 17, 2022 to week 17, 2023 (Source: WHO FLUNET ) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. Country (most recent week of report) Total number of specimens processed Total number of influenza-positive specimens Australia (17 of 2023) 56,472 846 Cambodia (14 of 2023) 1,157 41 China (17 of 2023) 368,936 110,241 Fiji (14 of 2023) 1,013 278 Japan (15 of 2023) - 1,836 Lao People’s Democratic Republic (16 of 2023) 1,682 129 Malaysia (17 of 2023) 14,432 3,118 Mongolia (13 of 2023) 6,881 1,485 New Caledonia - - New Zealand - - Papua New Guinea - - Philippines (17 of 2023) 1,479 83 Republic of Korea (17 of 2023) 5,013 450 Singapore (17 of 2023) 4,529 1,002 Viet Nam (16 of 2023) 36 12 Influenza Situation Update| 2 The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 17 of 2023, sentinel hospitals in the northern provinces reported ILI% of 3.1%, lower than the last week (3.4%), and higher than the same week of 2020-2022 (1.8%, 2.4%, and 1.7%). (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in northern China, 2020-2023 (Source: China National Influenza Center) Mongolia During week 17 of 2023, the ILI activity in Mongolia increased to 46 ILI cases per 10,000 population. This is above the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Influenza Situation Update| 3 Republic of Korea In week 17 2023, overall weekly influenza-like illness (ILI) rate was 23.0% per 1,000 outpatient visits, which was higher than 19.9‰ recorded in the previous week. (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korea Disease Control and Prevention Agency) Sentinel influenza surveillance Japan In week 17 of 2023, the number of cases reported weekly by sentinel hospital sites remained low in Japan. The number of cases in 2023 was consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) ILI (p er 1 ,0 00 O ut pa tie nt C on su lta tio ns ) Influenza Situation Update| 4 Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed that the overall seasonal influenza activity in Hong Kong remained active. In week 17, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 5.2 ILI cases per 1,000 consultations, which was higher than 3.3 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 49.3 ILI cases per 1,000 consultations, which was higher than 45.0 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private doctors, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) China (South) - ILI Surveillance During week 17, the percentage of outpatient or emergency visits for ILI (ILI%) at national sentinel hospitals in southern provinces was 5.2%, lower than the last week (6.0%), and higher than the same week of 2020-2022(2.3%, 3.7% and 3.1%) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2023 (Source: China National Influenza Center) Influenza Situation Update| 5 Singapore – Acute Respiratory Infection (ARI) Surveillance In week 17 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,677 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.5. The overall positivity rate for influenza among ILI samples (n= 1403) in the community was 20.5% in the past 4 weeks. Of the 421 specimens tested positive for influenza in Mar 2023, 258 were positive for Influenza A(H3N2) (61.3%), 94 were positive for Influenza A(pH1N1) (22.3%), 1 was positive for Influenza A(LVT) (0.2%), and 68 were positive for Influenza B (16.2%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 (Source: Singapore Ministry of Health) Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 (Source: Singapore Ministry of Health) Lao PDR During week 17 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 45 cases higher than the previous week. There were 141 samples tested for influenza in week 17, 2023. Influenza A/pdmH1N1 was identified (n=16) (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Influenza Situation Update| 6 Cambodia In week 17 of 2023, the Ministry of Health received data from all seven sentinel sites in Cambodia. The number of ILI cases in Cambodia slightly increased between week 16 (129 cases) and week 17 (144 cases) . 6.25% positivity rate was reported for this week (Figure 12). Figure 12: Number of ILI cases from seven sentinel sites and influenza positivity rate by the week, of 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year to 30 April 2023, there have been 32,047 notifications of laboratory-confirmed influenza reported to the National Notifiable Diseases Surveillance System in Australia. There were 6,098 laboratory-confirmed influenza notifications with a diagnosis date this fortnight (Monday 17 April to Sunday 30 April 2023), a decrease compared to 6,853 notifications in the previous fortnight. From March 2023 the number of notifications of laboratory-confirmed influenza has gradually increased. The number of notifications year-to-date is higher than the 5-year average, but lower than observed in the same period in 2019 (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2016 to 2023 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) Influenza Situation Update| 7 New Zealand – Influenza like Illness In the week ending of 30 April 2023, the influenza like illness (ILI) general practitioner consultation(Figure 14) rates decreased compared to the previous week ear. National influenza-like illness (ILI) activity in the community remains at low expected levels for this time of year. However, in Counties Manukau, Tairawhiti, Lakes, and South Canterbury, ILI activity is above the national rate. Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2015-2023 (Source: New Zealand Institute of Environmental Science and Research) Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 17 of 2023, 18 out of 21 PICs reported ILI surveillance data. No reports are available for American Samoa, Guam, and Nauru. The following countries reported increased influenza-like illness activity: Kiribati, New Caledonia, Niue and Tuvalu (Figure 15). Influenza Situation Update| 8 Influenza Situation Update| 9 Influenza Situation Update| 10 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. 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Bi-weekly Influenza Situation Update 24 May 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 19 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 19 of 2023 have been Influenza A(H1N1)pdm09 (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1, 2023 to week 19, 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, Week 19, 2022 to week 19, 2023 (Source: WHO FLUNET ) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an Country (most recent week of report) Total number of specimens processed Total number of influenza-positive specimens Australia (19 of 2023) 67,443 1,056 Cambodia (18 of 2023) 1,390 62 China (19 of 2023) 433,790 116,001 Fiji (14 of 2023) 1,013 278 Japan (18 of 2023) - 2,192 Lao People’s Democratic Republic (18 of 2023) 1,899 157 Malaysia (19 of 2023) 16,168 3,273 Mongolia (13 of 2023) 6,881 1,485 New Caledonia - - New Zealand - - Papua New Guinea - - Philippines (19 of 2023) 1,684 94 Republic of Korea (19 of 2023) 5,617 525 Singapore (19 of 2023) 5,162 1,110 Viet Nam (17 of 2023) 37 12 Influenza Situation Update| 2 acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 19 of 2023, sentinel hospitals in the northern provinces reported ILI% of 3.4%, lower than the last week (3.5%), and higher than the same week of 2020-2022 (1.9%, 2.4%, and 1.6%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in northern China, 2020-2023 (Source: China National Influenza Center) Mongolia During week 19 of 2023, the ILI activity in Mongolia decreased to 39 ILI cases per 10,000 population. This is above the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Influenza Situation Update| 3 Republic of Korea In week 19 2023, the overall weekly influenza-like illness (ILI) rate was 23.4% per 1,000 outpatient visits, which was lower than 23.7‰ recorded in the previous week (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korea Disease Control and Prevention Agency) Sentinel influenza surveillance Japan In week 19 of 2023, the number of cases reported weekly by sentinel hospital sites remained low in Japan. The number of cases in 2023 was consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) ILI (p er 1 ,0 00 O ut pa tie nt C on su lta tio ns ) Influenza Situation Update| 4 Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed a decreasing trend in the overall seasonal influenza activity. In week 19, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 3.4 ILI cases per 1,000 consultations, which was lower than 3.8 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 45.5 ILI cases per 1,000 consultations, which was lower than 56.8 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private doctors, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) China (South) - ILI Surveillance During week 19, the percentage of outpatient or emergency visits for ILI (ILI%) at national sentinel hospitals in southern provinces was 6.7%, higher than the last week (6.3%), and higher than the same week of 2020-2022(2.7%, 3.7%, and 3.0%) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2023 (Source: China National Influenza Center) Influenza Situation Update| 5 Singapore – Acute Respiratory Infection (ARI) Surveillance In week 19 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,631 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.5. The overall positivity rate for influenza among ILI samples (n= 1,365) in the community was 17.4% in the past 4 weeks. Of the 288 specimens tested positive for influenza in April 2023, 199 were positive for Influenza A(H3N2) (69.1%), 57 were positive for Influenza A(pH1N1) (19.8%), 1 was positive for Influenza A(LVT) (0.3%), and 31 were positive for Influenza B (10.8%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 (Source: Singapore Ministry of Health) Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 (Source: Singapore Ministry of Health) Lao PDR During week 19 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 30 cases higher than the previous week. There were 81 samples tested for influenza in week 19, 2023. Influenza A/pdmH1N1 was identified (n=22) (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Influenza Situation Update| 6 Cambodia In week 19 of 2023, the Ministry of Health received data from all seven sentinel sites in Cambodia. The number of ILI cases in Cambodia slightly increased between week 18 (143 cases) and week 19 (152 cases) of 2023 (Figure 12). The positivity rate was 5.26% for this week. Figure 12: Number of ILI cases from seven sentinel sites and influenza positivity rate by the week, of 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year to 14 May 2023, there have been 40,138 notifications of laboratory-confirmed influenza reported to the National Notifiable Diseases Surveillance System in Australia. There were 8,173 laboratory-confirmed influenza notifications with a diagnosis date this fortnight (Monday 1 May to Sunday 14 May 2023), an increase compared to 6,159 notifications in the previous fortnight. From March 2023 the number of notifications of laboratory-confirmed influenza has gradually increased. The number of notifications year-to-date is higher than the 5-year average, but lower than observed in the same period in 2019 (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2016 to 2023 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) Influenza Situation Update| 7 New Zealand – Influenza like Illness In the week ending on 14 May 2023, the influenza like illness (ILI) general practitioner consultation (Figure 14) rates increased compared to the previous week. National influenza-like illness (ILI) activity in the community increased in the week ending 14 but remains at expected low levels for this time of year. However, in Counties Manukau and Lakes, ILI activity is above the national rate. Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2015-2023 (Source: New Zealand Institute of Environmental Science and Research) Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 19 of 2023, 18 out of 21 PICs reported ILI surveillance data. Only 15 out of 18 PICS reported updated data. No reports are available for American Samoa, Guam, and Nauru, and no updates from French Polynesia, Tokelau, and Tuvalu. The following countries reported increased influenza-like illness activity: Fiji, Tuvalu, and Vanuatu (Figure 15). Influenza Situation Update| 8 Influenza Situation Update| 9 Influenza Situation Update| 10 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. Arabic, Chinese, English, French, Russian, Spanish Influenza Situation Update| 11

Influenza Situation Update| 1 Bi-weekly Influenza Situation Update 7 June 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 21 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 21 of 2023 have been Influenza A(H1N1)pdm09 (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1, 2023 to week 21, 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, Week 21, 2022 to week 21, 2023 (Source: WHO FLUNET ) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Country (most recent week of report) Total number of specimens processed Total number of influenza-positive specimens Australia (21 of 2023) 78,881 1,466 Cambodia (20 of 2023) 1,561 103 China (21 of 2023) 500,309 117,742 Fiji (15 of 2023) 1,498 448 Japan (20 of 2023) - 2,296 Lao People’s Democratic Republic (21 of 2023) 2,202 222 Malaysia (21 of 2023) 18,003 3,473 Mongolia (21 of 2023) 9,542 1,527 New Caledonia - - New Zealand - - Papua New Guinea - - Philippines (19 of 2023) 1,684 94 Republic of Korea (21 of 2023) 6,235 618 Singapore (21 of 2023) 5,838 1,216 Viet Nam (17 of 2023) 37 12 Influenza Situation Update| 2 Bi-weekly Influenza Situation Update 7 June 2023 Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 21 of 2023, sentinel hospitals in the northern provinces reported ILI% of 4.1%, the same as the last week (4.1%), and higher than the same week of 2020-2022 (1.9%, 2.9%, and 1.7%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in northern China, 2020-2023 (Source: China National Influenza Center) Mongolia During week 20 of 2023, the ILI activity in Mongolia decreased to 28 ILI cases per 10,000 population. This is above the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Influenza Situation Update| 3 Bi-weekly Influenza Situation Update 7 June 2023 Republic of Korea In week 21 2023, the overall weekly influenza-like illness (ILI) rate was 25.7% per 1,000 outpatient visits, which was the same as the rate recorded in the previous week (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korea Disease Control and Prevention Agency) Sentinel influenza surveillance Japan In week 20 of 2023, the number of cases reported weekly by sentinel hospital sites remained low in Japan. The number of cases in 2023 was consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) IL I ( p er 1 ,0 00 O u tp at ie n t C o n su lt at io n s) Influenza Situation Update| 4 Bi-weekly Influenza Situation Update 7 June 2023 Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed a decreasing trend in the overall seasonal influenza activity. In week 21, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 2.3 ILI cases per 1,000 consultations, which was lower than 3.1 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 35.7 ILI cases per 1,000 consultations, which was lower than 41.6 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private doctors, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) China (South) - ILI Surveillance During week 21, the percentage of outpatient or emergency visits for ILI (ILI%) at national sentinel hospitals in southern provinces was 6.5%, lower than the last week (7.2%), and higher than the same week of 2020-2022 (3.0%, 4.2%, and 4.0%) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2023 (Source: China National Influenza Center) Influenza Situation Update| 5 Bi-weekly Influenza Situation Update 7 June 2023 Singapore – Acute Respiratory Infection (ARI) Surveillance In week 21 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,300 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.5. The overall positivity rate for influenza among ILI samples (n=1,309) in the community was 16.3% in the past 4 weeks. Of the 288 specimens tested positive for influenza in April 2023, 199 were positive for Influenza A(H3N2) (69.1%), 57 were positive for Influenza A(pH1N1) (19.8%), 1 was positive for Influenza A(LVT) (0.3%), and 31 were positive for Influenza B (10.8%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 (Source: Singapore Ministry of Health) Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 (Source: Singapore Ministry of Health) Lao PDR During week 21 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 57 cases higher than previous week. There were 58 samples tested for influenza in week 21, 2023. Influenza A/pdmH1N1 was identified (n=12) (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Cambodia In week 20 of 2023, the Ministry of Health received data from all seven sentinel sites in Cambodia. During this period, the number of ILI cases in Cambodia slightly increased between week 19 (161 cases) and week 20 (173 cases) of 2023. There was 2 (12.5%) samples tested positive for influenza virus (Figure 12). Proportion of weekly influenza positive is fluctuated in 2023. Influenza Situation Update| 6 Bi-weekly Influenza Situation Update 7 June 2023 Figure 12: Number of ILI cases from seven sentinel sites and influenza positivity rate by the week, of 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year to 28 May 2023, there have been 57,816 notifications of laboratory-confirmed influenza reported to the National Notifiable Diseases Surveillance System in Australia. There were 17,277 laboratory-confirmed influenza notifications with a diagnosis date this fortnight (Monday 15 May to Sunday 28 May 2023), a steep increase compared to 8,236 notifications in the previous fortnight. From March 2023 the number of notifications of laboratory-confirmed influenza has gradually increased. The number of notifications year-to-date is higher than the 5-year average, and now slightly higher than observed in the same period in 2019 (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2016 to 2023 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) Influenza Situation Update| 7 Bi-weekly Influenza Situation Update 7 June 2023 New Zealand – Influenza like Illness In the week ending on 28 May 2023, the influenza like illness (ILI) general practitioner consultation (Figure 14) rates increased compared to the previous week. The rate is similar to that observed at this time in 2022 and the 2015-2019 average. However, in Counties Manukau, MidCentlra, Waitemata, and Hawke’s Bay, ILI activity is above the national rate. Influenza B and A(H1N1) are the viruses most commonly detected in community surveillance in recent weeks. Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2015-2023 (Source: New Zealand Institute of Environmental Science and Research) Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 21 of 2023, 18 out of 21 PICs reported ILI surveillance data. 17 out of 18 PICs reported updated data. No reports are available for American Samoa, Guam, and Nauru, and no updates from French Polynesia and Tokelau. The following countries reported increased influenza-like illness activity: Micronesia (Federated States of), Samoa, and Vanuatu. (Figure 15). In Vanuatu, as of 01 June 2023, the National Surveillance Unit recorded 533 new ILI cases between the 22 May to 28 May 2023. Testing confirmed five cases of Influenza B and one case of Influenza A H1N1. The total suspected ILI cases recorded in 2023 is 7,601. (Source: PACNET on 30 May 2023). 0 50 100 1 4 7 101316192225283134374043464952 Cook Islands ILI Trend 2019 -2023 (WK 21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 500 1000 1500 2000 1 4 7 101316192225283134374043464952 Fiji ILI Trend 2019 -2023 ( WK 21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Baseline 0 500 1000 1 5 9 13 17 21 25 29 33 37 41 45 49 C a se s Epi week French Polynesia ILI trend 2019 - 2023 (WK 12) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 0 500 1000 1500 1 5 9 13 17 21 25 29 33 37 41 45 49 C a se s Epi week FSM ILI trend 2019 - 2023 (WK20) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 Influenza Situation Update| 8 Bi-weekly Influenza Situation Update 7 June 2023 -500 500 1500 2500 3500 1 5 9 13 17 21 25 29 33 37 41 45 49 53 C a se s Epi week Kiribati ILI trend 2019-2023 (WK21) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 50 100 150 200 250 1 4 7 101316192225283134374043464952 C a se s Epi week Marshall Islands ILI trend 2019 -2023 ( WK 21) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 50 100 150 1 5 9 13 17 21 25 29 33 37 41 45 49 53 C a se s EPi week CNMI ILI Trend 2019 -2023 (WK 21) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 ILI 2022 -100 100 300 500 700 1 4 7 101316192225283134374043464952 C a se s Epi week New Caledonia ILI Trend 2019 -2023 (WK 21) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 50 100 150 200 1 4 7 101316192225283134374043464952 C a se s Epi week Palau ILI Trend 2019 - 2023 (WK 21) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 5 10 15 20 25 1 5 9 13 17 21 25 29 33 37 41 45 49 C as es Epi week Niue ILI Trend 2019 - 2023 (WK21) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 1 2 3 4 5 1 4 7 1 0 1 3 1 6 1 9 2 2 2 5 2 8 3 1 3 4 3 7 4 0 4 3 4 6 4 9 5 2 C a se s Epi week Pitcairn Islands ILI Trend 2019 - 2023 (WK 21) ILI 2019 ILI 2020 ILI 2021 ILI 2022 ILI 2023 0 1000 2000 3000 4000 1 5 9 13 17 21 25 29 33 37 41 45 49 53 C a se s Epi week Samoa ILI Trend 2019 -2023 ( WK 21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Influenza Situation Update| 9 Bi-weekly Influenza Situation Update 7 June 2023 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) 0 1000 2000 3000 4000 1 4 7 101316192225283134374043464952 C a se s Epi week Solomon Islands ILI Trend 2019 - 2023 (WK21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 10 20 30 40 1 5 9 13 17 21 25 29 33 37 41 45 49 53 C a se s Epi week Tokelau ILI Trend 2019 -2023 (WK 21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 100 200 300 400 500 600 700 800 1 5 9 13 17 21 25 29 33 37 41 45 49 C a se s Epi week Tonga ILI trend 2019 -2023 (WK 21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 20 40 60 80 100 120 1 4 7 101316192225283134374043464952 Tuvalu ILI trend 2019 -2023 (WK 21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 500 1000 1500 2000 1 4 7 101316192225283134374043464952 C a se s Epi week Vanuatu ILI Trend 2019 - 2023 (WK21) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 200 400 600 800 1 5 9 13 17 21 25 29 33 37 41 45 49 53 C a se s Epi week Wallis & Futuna ILI trend 2019 to 2023 (WK21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Influenza Situation Update| 10 Bi-weekly Influenza Situation Update 7 June 2023 Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. Arabic, Chinese, English, French, Russian, Spanish

Influenza Situation Update| 1 Bi-weekly Influenza Situation Update 21 June 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 23 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 23 of 2023 have been Influenza A(H1N1)pdm09 (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1, 2023 to week 23, 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, week 23, 2022 to week 23, 2023 (Source: WHO FLUNET ) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Country (most recent week of report) Total number of specimens processed Total number of influenza-positive specimens Australia (23 of 2023) 90,801 2,210 Cambodia (22 of 2023) 1,789 160 China (23 of 2023) 564,432 118,329 Fiji (20 of 2023) 1,914 461 Japan (22 of 2023) - 2,405 Lao People’s Democratic Republic (23 of 2023) 2,383 241 Malaysia (23 of 2023) 19,709 3,703 Mongolia (21 of 2023) 9,542 1,527 New Caledonia - - New Zealand (23 of 2023) 1,117 236 Papua New Guinea - - Philippines (23 of 2023) 2,200 170 Republic of Korea (23 of 2023) 6,679 671 Singapore (23 of 2023) 6,300 1,291 Viet Nam (17 of 2023) 37 12 Influenza Situation Update| 2 Bi-weekly Influenza Situation Update 21 June 2023 Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 23 of 2023, sentinel hospitals in the northern provinces reported ILI% of 3.7%, lower than the last week (3.9%), and higher than the same week of 2020-2022 (2.0%, 3.1%, and 1.6%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in northern China, 2020-2023 (Source: China National Influenza Center) Mongolia During week 23 of 2023, the ILI activity in Mongolia decreased to 26 ILI cases per 10,000 population. This is above the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Influenza Situation Update| 3 Bi-weekly Influenza Situation Update 21 June 2023 Republic of Korea In week 23 of 2023, the overall weekly influenza-like illness (ILI) rate was 18.1 per 1,000 outpatient visits, which was lower than the rate recorded in the previous week (21.5) (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korea Disease Control and Prevention Agency) Sentinel influenza surveillance Japan In week 22 of 2023, the number of cases reported weekly by sentinel hospital sites remained low in Japan. The number of cases in 2023 is consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) IL I ( p er 1 ,0 0 0 O u tp at ie n t C o n su lt at io n s) Influenza Situation Update| 4 Bi-weekly Influenza Situation Update 21 June 2023 Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed a decreasing trend in the overall seasonal influenza activity. In week 23, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 1.9 ILI cases per 1,000 consultations, which was slightly lower than 2.0 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 27.7 ILI cases per 1,000 consultations, which was lower than 45.8 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private doctors, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) China (South) - ILI Surveillance During week 23, the percentage of outpatient or emergency visits for ILI (ILI%) at national sentinel hospitals in southern provinces was 5.8%, lower than the last week (6.3%), higher than the same week of 2020 and 2021 (3.0% and 4.3%) and the same as the same week of 2022 (5.8%) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2023 (Source: China National Influenza Center) Influenza Situation Update| 5 Bi-weekly Influenza Situation Update 21 June 2023 Singapore – Acute Respiratory Infection (ARI) Surveillance In week 23 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 1,913 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.5. The overall positivity rate for influenza among ILI samples (n=1,138) in the community was 15.8% in the past 4 weeks. Of the 241 specimens tested positive for influenza in May 2023, 162 were positive for Influenza A(H3N2) (67%), 56 were positive for Influenza A(pH1N1) (23%), and 23 were positive for Influenza B (10%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 (Source: Singapore Ministry of Health) Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 (Source: Singapore Ministry of Health) Lao PDR During week 23 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of influenza-like illness cases presenting at sentinel sites was 44 cases higher than the previous week. There were 55 samples tested for influenza in week 23, 2023. Influenza A/pdmH1N1 was identified (n=7) (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Influenza Situation Update| 6 Bi-weekly Influenza Situation Update 21 June 2023 Cambodia In week 22 of 2023, the Ministry of Health received data from 11 sentinel sites in Cambodia. During this period, the number of ILI cases in Cambodia remained steady between week 21 (194 cases) and week 22 (193 cases) of 2023. Of the 15 samples collected, 4 (26.7%) samples were positive for influenza A/H1N1pdm (Figure 12). The proportion of weekly influenza positive samples fluctuated in 2023. Figure 12: Number of ILI cases from seven sentinel sites and influenza positivity rate by the week, of 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year to 11 June 2023, there have been 85,986 notifications of laboratory-confirmed influenza reported to the National Notifiable Diseases Surveillance System in Australia. There were 27,540 laboratory-confirmed influenza notifications with a diagnosis date this fortnight (Monday 29 May to Sunday 11 June 2023), compared to 17,875 notifications in the previous fortnight. From March 2023 the number of notifications of laboratory-confirmed influenza has gradually increased. The number of notifications year-to-date is higher than the 5-year average, and higher than observed in the same period in 2019 (Figure 13). Influenza Situation Update| 7 Bi-weekly Influenza Situation Update 21 June 2023 Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2016 to 2023 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) New Zealand – ILI Surveillance In the week ending on 11 June 2023, the influenza-like illness (ILI) general practitioner consultation rates decreased compared to the previous week (10.6 per 1,000 compared to 12.3 per 1,000) (Figure 14). The rate is lower to that observed at this time in 2022 and the 2015-2019 average. County Manukau continues to record the highest rate of general practitioner ILI consultations, which is above the national rate and higher than usual for this time of year. Rates in MidCentral, Hawke’s Bay and Lakes also remain above the national rate. Influenza B and A(H1N1) are the viruses most commonly detected in community surveillance in recent weeks. Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2015-2023 (Source: New Zealand Institute of Environmental Science and Research) Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 23 of 2023, 18 out of 21 PICs reported ILI surveillance data. 15 out of 18 PICs reported updated data. No reports are available for American Samoa, Guam, and Nauru, and no updates from Federated States of Micronesia, Tokelau and Tuvalu. The following countries reported increased influenza-like illness activity in week 23 compared to the previous week: Fiji, Commonwealth of Northern Mariana Islands, Samoa, Solomon Islands and Tonga. (Figure 15). Influenza Situation Update| 8 Bi-weekly Influenza Situation Update 21 June 2023 In Palau, as of 19 June 2023, the Ministry of Health and Human Services reported a steep increase in influenza observed at the Belau National Hospital. Laboratory testing confirmed influenza B virus in 44 patients since 28 May. Most of the cases are children and adolescents aged 15 years and below. (Sources: PACNET on 20 June 2023 and Palau Ministry of Health & Human Services). 0 20 40 60 80 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 Cook Islands ILI Trend 2019 - 2023 (WK 23) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 500 1000 1500 2000 1 4 7 101316192225283134374043464952 Fiji ILI Trend 2019 - 2023 (WK 23) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Baseline 0 200 400 600 800 1 4 7 101316192225283134374043464952 C a se s Epi week French Polynesia ILI trend 2019 - 2023 (WK 23) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 0 200 400 600 800 1000 1200 1 4 7 1 0 1 3 1 6 1 9 2 2 2 5 2 8 3 1 3 4 3 7 4 0 4 3 4 6 4 9 5 2 C a se s Epi week FSM ILI trend 2019 - 2023 (WK20) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 500 1000 1500 2000 2500 3000 3500 1 4 7 1 0 1 3 1 6 1 9 2 2 2 5 2 8 3 1 3 4 3 7 4 0 4 3 4 6 4 9 5 2 C a se s Epi week Kiribati ILI trend 2019 - 2023 (WK23) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 50 100 150 200 250 1 4 7 101316192225283134374043464952 C a se s Epi week Marshall Islands ILI trend 2019 - 2023 (WK 23) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 Influenza Situation Update| 9 Bi-weekly Influenza Situation Update 21 June 2023 0 50 100 150 1 4 7 101316192225283134374043464952 C a se s Epi week CNMI ILI Trend 2019 - 2023 (WK 23) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 ILI 2022 0 200 400 600 1 4 7 101316192225283134374043464952 C a se s Epi week New Caledonia ILI Trend 2019 - 2023 (WK 23) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 50 100 150 200 1 5 9 13 17 21 25 29 33 37 41 45 49 53 C a se s Epi week Palau ILI Trend 2019 - 2023 (WK 23) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 5 10 15 20 25 1 5 9 13 17 21 25 29 33 37 41 45 49 C a se s Epi week Niue ILI Trend 2019 - 2023 (WK23) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 1 2 3 4 5 1 4 7 101316192225283134374043464952 C a se s Epi week Pitcairn Islands ILI Trend 2019 - 2023 (WK 23) ILI 2019 ILI 2020 ILI 2021 ILI 2022 ILI 2023 0 1000 2000 3000 4000 1 5 9 13 17 21 25 29 33 37 41 45 49 53 C a se s Epi week Samoa ILI Trend 2019 - 2023 ( WK 23) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 1000 2000 3000 4000 1 4 7 101316192225283134374043464952 C a se s Epi week Solomon Islands ILI Trend 2019 - 2023 (WK23) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 10 20 30 40 1 4 7 1 0 1 3 1 6 1 9 2 2 2 5 2 8 3 1 3 4 3 7 4 0 4 3 4 6 4 9 5 2 C a se s Epi week Tokelau ILI Trend 2019 - 2023 (WK 22) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Influenza Situation Update| 10 Bi-weekly Influenza Situation Update 21 June 2023 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. Arabic, Chinese, English, French, Russian, Spanish 0 100 200 300 400 500 600 700 800 1 5 9 13 17 21 25 29 33 37 41 45 49 C a se s Epi week Tonga ILI trend 2019 -2023 (WK 23) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 20 40 60 80 100 120 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 Epi week Tuvalu ILI trend 2019 -2023 (WK 21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 500 1000 1500 2000 1 4 7 101316192225283134374043464952 C a se s Epi week Vanuatu ILI Trend 2019 - 2023 (WK23) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 200 400 600 800 1 4 7 101316192225283134374043464952 C a se s Epi week Wallis & Futuna ILI trend 2019 - 2023 (WK23) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022

Influenza Situation Update| 1 Bi-weekly Influenza Situation Update 5 July 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 25 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 25 of 2023 have been Influenza A (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1 to week 25, 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, week 25, 2022 to week 25, 2023 (Source: WHO FLUNET ) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Country (most recent week of report) Total number of specimens processed Total number of influenza-positive specimens Australia (25 of 2023) 102,422 2,991 Cambodia (25 of 2023) 2,181 260 China (25 of 2023) 615,193 118,509 Fiji (24 of 2023) 2,252 463 Japan (25 of 2023) - 2,670 Lao People’s Democratic Republic (25 of 2023) 2,630 261 Malaysia (24 of 2023) 20,674 3,815 Mongolia (25 of 2023) 10,092 1,532 New Caledonia - - New Zealand (25 of 2023) 1,264 265 Papua New Guinea - - Philippines (24 of 2023) 2,293 181 Republic of Korea (25 of 2023) 7,213 713 Singapore (25 of 2023) 6,743 1,382 Viet Nam (20 of 2023) 597 235 Influenza Situation Update| 2 Bi-weekly Influenza Situation Update 5 July 2023 Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 25 of 2023, sentinel hospitals in the northern provinces reported ILI% of 3.4%, lower than the last week (3.6%), and higher than the same week of 2020-2022 (2.4%, 2.7%, and 1.8%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in northern China, 2020-2023 (Source: China National Influenza Center) Mongolia During week 25 of 2023, the ILI activity in Mongolia decreased to 18 ILI cases per 10,000 population. This is below the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Influenza Situation Update| 3 Bi-weekly Influenza Situation Update 5 July 2023 Republic of Korea In week 25 of 2023, the overall weekly influenza-like illness (ILI) rate was 15.0 per 1,000 outpatient visits, which was lower than the rate recorded in the previous week (15.7) (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korea Disease Control and Prevention Agency) Sentinel influenza surveillance Japan In week 24 of 2023, the number of cases reported weekly by sentinel hospital sites remained low in Japan. The number of cases in 2023 is consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) IL I ( p er 1 ,0 0 0 O u tp at ie n t C o n su lt at io n s) Influenza Situation Update| 4 Bi-weekly Influenza Situation Update 5 July 2023 Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed an increase in the overall seasonal influenza activity. In week 25, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 2.2 ILI cases per 1,000 consultations, which was higher than 2.1 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 39.2 ILI cases per 1,000 consultations, which was higher than 35.9 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private medical practitioner clinics, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) China (South) - ILI Surveillance During week 25, the percentage of outpatient or emergency visits for ILI (ILI%) at national sentinel hospitals in southern provinces was 5.5%, the same as the last week (5.5%), higher than the same week of 2020 and 2021 (3.4% and 4.0%) and the lower than the same week of 2022 (7.5%) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2023 (Source: China National Influenza Center) Influenza Situation Update| 5 Bi-weekly Influenza Situation Update 5 July 2023 Singapore – Acute Respiratory Infection (ARI) Surveillance In week 25 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 1,885 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.4%. The overall positivity rate for influenza among ILI samples (n= 905) in the community was 18.2% in the past 4 weeks. Of the 241 specimens tested positive for influenza in May 2023, 162 were positive for Influenza A(H3N2) (67%), 56 were positive for Influenza A(pH1N1) (23%), and 23 were positive for Influenza B (10%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 (Source: Singapore Ministry of Health) Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 (Source: Singapore Ministry of Health) Lao PDR During week 25 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of influenza-like illness cases presenting at sentinel sites was 32 cases higher than the previous week. There were 78 samples tested for influenza in week 25, 2023. Influenza A/pdmH1N1 was identified (n=6) (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Influenza Situation Update| 6 Bi-weekly Influenza Situation Update 5 July 2023 Cambodia In week 25 of 2023, the Ministry of Health received data from 12 sentinel sites in Cambodia. During this period, the number of ILI cases in Cambodia decreased between week 24 (204 cases) and week 25 (177 cases) of 2023. Of the 20 samples collected, 7 (35.0%) samples were positive for influenza A/H1N1pdm (Figure 12). The proportion of weekly influenza positive samples fluctuated in 2023. Figure 12: Number of ILI samples from sentinel sites and influenza positivity rate by the week, of 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year-to-date (1 January to 25 June 2023), there have been 116,473 notifications of laboratory- confirmed influenza reported to the National Notifiable Diseases Surveillance System in Australia. There were 29,315 laboratory-confirmed influenza notifications with a diagnosis date this fortnight (Monday 12 June to Sunday 25 June 2023), compared to 27,540 notifications in the previous fortnight. From March 2023 the number of notifications of laboratory-confirmed influenza has gradually increased. The number of notifications year-to-date is higher than the 5-year average, and higher than observed in the same period in 2019 (Figure 13). Influenza Situation Update| 7 Bi-weekly Influenza Situation Update 5 July 2023 Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2016 to 2023 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) New Zealand – ILI Surveillance In the week ending on 25 June 2023, the influenza-like illness (ILI) general practitioner consultation rates increased compared to the previous week (17.6 per 100,000 compared to 14.9 per 100,000) (Figure 14). The national rate is lower than that observed at this time in 2022 and the 2015-2019. County Lakes recorded the highest rate of general practitioner ILI consultations, which is above the national rate and higher than usual for this time of year. Rates in Manukau and Waitemata also remain above the national rate. Influenza B and A(H1N1) are the viruses most commonly detected in community surveillance in recent weeks. Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2015-2023 (Source: New Zealand Institute of Environmental Science and Research) Influenza Situation Update| 8 Bi-weekly Influenza Situation Update 5 July 2023 Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 25 of 2023, 18 out of 21 PICs reported ILI surveillance data. 16 out of 18 PICs reported updated data. No reports are available for American Samoa, Guam, and Nauru, and no updates from Federated States of Micronesia and Tuvalu. The following countries reported increased influenza-like illness activity in week 25 compared to the previous week: Republic of the Marshall Islands, Fiji and Vanuatu. (Figure 15). 0 10 20 30 40 50 60 70 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Cook Islands ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 200 400 600 800 1000 1200 1400 1600 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Fiji ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Baseline 0 100 200 300 400 500 600 700 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 C a se s Epi week French Polynesia ILI trend 2019 - 2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 0 200 400 600 800 1000 1200 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 C a se s Epi week FSM ILI trend 2019 - 2023 (WK 20) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 500 1000 1500 2000 2500 3000 3500 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Kiribati ILI trend 2019-2023 (WK 24) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 50 100 150 200 250 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Marshall Islands ILI trend 2019-2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 Influenza Situation Update| 9 Bi-weekly Influenza Situation Update 5 July 2023 0 20 40 60 80 100 120 140 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s EPi week CNMI ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 ILI 2022 0 100 200 300 400 500 600 700 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week New Caledonia ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 0 20 40 60 80 100 120 140 160 180 200 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Palau ILI Trend 2019 - 2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 5 10 15 20 25 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 C a se s Epi week Niue ILI Trend 2019 - 2023 (WK25) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 1 2 3 4 5 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 C a se s Epi week Pitcairn Islands ILI Trend 2019 - 2023 (WK 25) ILI 2019 ILI 2020 ILI 2021 ILI 2022 ILI 2023 0 500 1000 1500 2000 2500 3000 3500 4000 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Samoa ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 500 1000 1500 2000 2500 3000 3500 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Solomon Islands ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 0 5 10 15 20 25 30 35 40 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Tokelau ILI Trend 2019 -2023 (WK 24) ILI 2023 ILI 2019 ILI 2020 ILI 2021 Influenza Situation Update| 10 Bi-weekly Influenza Situation Update 5 July 2023 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. Arabic, Chinese, English, French, Russian, Spanish 0 100 200 300 400 500 600 700 800 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 C a se s Epi week Tonga ILI trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 0 20 40 60 80 100 120 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 Tuvalu ILI trend 2019 -2023 (WK 21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 200 400 600 800 1000 1200 1400 1600 1800 2000 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Vanuatu ILI Trend 2019 - 2023 (WK25) ILI 2023 ILI 2020 ILI 2021 ILI 2019 0 100 200 300 400 500 600 700 800 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Wallis & Futuna ILI trend 2019 to 2023 (WK25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022

Bi-weekly Influenza Situation Update 19 July 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 27 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 27 of 2023 have been Influenza A (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1 to week 27, 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, week 27, 2022 to week 27, 2023 (Source: WHO FLUNET ) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Country (most recent week of report) Total number of specimens processed Total number of influenza-positive specimens Australia (27 of 2023) 114,004 4,288 Cambodia (27 of 2023) 2,376 313 China (27 of 2023) 678,007 119,039 Fiji (24 of 2023) 2,252 463 Japan (26 of 2023) - 2,767 Lao People’s Democratic Republic (27 of 2023) 3,020 277 Malaysia (27 of 2023) 23,354 4,271 Mongolia (25 of 2023) 10,092 1,532 New Caledonia - - New Zealand (27 of 2023) 1,444 317 Papua New Guinea - - Philippines (27 of 2023) 2,691 252 Republic of Korea (27 of 2023) 7,803 745 Singapore (27 of 2023) 7,146 1,473 Viet Nam (20 of 2023) 597 235 Influenza Situation Update| 2 Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 27 of 2023, sentinel hospitals in the northern provinces reported ILI% of 2.9%, lower than the last week (3.1%), and higher than the same week of 2020-2022 (2.0%, 2.5%, and 1.9%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in northern China, 2020-2023 (Source: China National Influenza Center) Mongolia During week 26 of 2023, the ILI activity in Mongolia decreased to 8 ILI cases per 10,000 population. This is below the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Influenza Situation Update| 3 Republic of Korea In week 27 of 2023, the overall weekly influenza-like illness (ILI) rate was 16.3 per 1,000 outpatient visits, which was similar to the rate recorded in the previous week (16.1) (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korea Disease Control and Prevention Agency) Sentinel influenza surveillance Japan In week 26 of 2023, the number of cases reported weekly by sentinel hospital sites remained low in Japan. The number of cases in 2023 is consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) ILI (p er 1 ,0 00 O ut pa tie nt C on su lta tio ns ) Influenza Situation Update| 4 Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed an increase in the overall seasonal influenza activity. In week 27, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 2.6 ILI cases per 1,000 consultations, which was higher than 2.1 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 33.4 ILI cases per 1,000 consultations, which was slightly higher than 32.3 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private medical practitioner clinics, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) China (South) - ILI Surveillance During week 27, the percentage of outpatient or emergency visits for ILI (ILI%) at national sentinel hospitals in southern provinces was 4.7%, lower than the last week (5.0%), higher than the same week of 2020 and 2021 (2.8% and 3.7%) and the lower than the same week of 2022 (5.5%) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2023 (Source: China National Influenza Center) Influenza Situation Update| 5 Singapore – Acute Respiratory Infection (ARI) Surveillance In week 27 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,211 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.3%. The overall positivity rate for influenza among ILI samples (n= 846) in the community was 21.5% in the past 4 weeks. Of the 176 specimens tested positive for influenza in Jun 2023, 103 were positive for Influenza A(H3N2) (58.5%), 60 were positive for Influenza A(pH1N1) (34.1%), and 12 were positive for Influenza B (6.8%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 (Source: Singapore Ministry of Health) Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 (Source: Singapore Ministry of Health) Lao PDR During week 27 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of influenza-like illness cases presenting at sentinel sites was 33 cases higher than the previous week. There were 100 samples tested for influenza in week 27, 2023. Influenza A/pdmH1N1 was identified (n=3) (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Influenza Situation Update| 6 Cambodia In week 26 of 2023, the Ministry of Health received data from 7 sentinel sites in Cambodia. During this period, the number of ILI cases in Cambodia decreased slightly between week 25 (175 cases) and week 26 (165 cases) of 2023. Of the 13 samples collected, 6 (46.2%) samples were positive for influenza A/H1N1pdm (Figure 12). The proportion of weekly influenza positive samples fluctuated in 2023. Figure 12: Number of ILI samples from sentinel sites and influenza positivity rate by the week, of 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year-to-date (1 January to 9 July 2023), there have been 149,989 notifications of laboratory- confirmed influenza reported to the National Notifiable Diseases Surveillance System in Australia. There were 32,132 laboratory-confirmed influenza notifications with a diagnosis date this fortnight (Monday 26 June to Sunday 9 July 2023), compared to 30,255 notifications in the previous fortnight. From March 2023 the number of notifications of laboratory-confirmed influenza has gradually increased. The number of notifications year-to-date is higher than the 5-year average, and higher than observed in the same period in 2019 (Figure 13). Influenza Situation Update| 7 Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2016 to 2023 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) New Zealand – ILI Surveillance In the week ending on 2 July 2023, the influenza-like illness (ILI) general practitioner consultation rates increased compared to the previous week (18.35 per 100,000 compared to 17.6 per 100,000) (Figure 14). The national rate is lower than that observed at this time in 2022 and the 2015-2019 period. County Lakes recorded the highest rate of general practitioner ILI consultations, which is above the national rate and higher than usual for this time of year. Rates in Manukau and MidCentral also remain above the national rate. Influenza B and A(H1N1) are the viruses most commonly detected in community surveillance in recent weeks. Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2015-2023 (Source: New Zealand Institute of Environmental Science and Research) Influenza Situation Update| 8 Pacific Island Countries and Areas (PICs) - ILI Surveillance There have been no updates since the previous report. In week 25 of 2023, 18 out of 21 PICs reported ILI surveillance data. 16 out of 18 PICs reported updated data. No reports are available for American Samoa, Guam, and Nauru, and no updates from Federated States of Micronesia and Tuvalu. The following countries reported increased influenza-like illness activity in week 25 compared to the previous week: Republic of the Marshall Islands, Fiji and Vanuatu. (Figure 15). 0 10 20 30 40 50 60 70 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Cook Islands ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 200 400 600 800 1000 1200 1400 1600 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Fiji ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Baseline 0 100 200 300 400 500 600 700 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 Ca se s Epi week French Polynesia ILI trend 2019 - 2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 0 200 400 600 800 1000 1200 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 Ca se s Epi week FSM ILI trend 2019 - 2023 (WK 20) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 500 1000 1500 2000 2500 3000 3500 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Ca se s Epi week Kiribati ILI trend 2019-2023 (WK 24) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 50 100 150 200 250 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Ca se s Epi week Marshall Islands ILI trend 2019-2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 Influenza Situation Update| 9 0 20 40 60 80 100 120 140 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Ca se s EPi week CNMI ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 ILI 2022 0 100 200 300 400 500 600 700 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Ca se s Epi week New Caledonia ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 0 20 40 60 80 100 120 140 160 180 200 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Ca se s Epi week Palau ILI Trend 2019 - 2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 5 10 15 20 25 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 Ca se s Epi week Niue ILI Trend 2019 - 2023 (WK25) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 1 2 3 4 5 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 Ca se s Epi week Pitcairn Islands ILI Trend 2019 - 2023 (WK 25) ILI 2019 ILI 2020 ILI 2021 ILI 2022 ILI 2023 0 500 1000 1500 2000 2500 3000 3500 4000 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Ca se s Epi week Samoa ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 500 1000 1500 2000 2500 3000 3500 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Ca se s Epi week Solomon Islands ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 0 5 10 15 20 25 30 35 40 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Ca se s Epi week Tokelau ILI Trend 2019 -2023 (WK 24) ILI 2023 ILI 2019 ILI 2020 ILI 2021 Influenza Situation Update| 10 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2023-2024 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. Arabic, Chinese, English, French, Russian, Spanish 0 100 200 300 400 500 600 700 800 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 Ca se s Epi week Tonga ILI trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 0 20 40 60 80 100 120 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 Tuvalu ILI trend 2019 -2023 (WK 21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 200 400 600 800 1000 1200 1400 1600 1800 2000 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Ca se s Epi week Vanuatu ILI Trend 2019 - 2023 (WK25) ILI 2023 ILI 2020 ILI 2021 ILI 2019 0 100 200 300 400 500 600 700 800 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Ca se s Epi week Wallis & Futuna ILI trend 2019 to 2023 (WK25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022

Influenza Situation Update| 1 Bi-weekly Influenza Situation Update 2 August 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 29 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 29 of 2023 have been Influenza A (Figure 1). Caution should be taken when interpreting these data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1 to week 29, 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, week 29, 2022 to week 29, 2023 (Source: WHO FLUNET ) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Country (most recent week of report) Total number of specimens processed Total number of influenza-positive specimens Australia (29 of 2023) 123,904 5,139 Cambodia (28 of 2023) 2,520 337 China (29 of 2023) 735,188 119,934 Fiji (24 of 2023) 2,252 463 Japan (28 of 2023) - 2,948 Lao People’s Democratic Republic (29 of 2023) 3,375 283 Malaysia (29 of 2023) 25,192 4,637 Mongolia (27 of 2023) 10,289 1,532 New Caledonia - - New Zealand (29 of 2023) 1,620 352 Papua New Guinea - - Philippines (29 of 2023) 2,903 270 Republic of Korea (29 of 2023) 8,487 794 Singapore (29 of 2023) 7,662 1,609 Viet Nam (29 of 2023) 769 255 Influenza Situation Update| 2 Bi-weekly Influenza Situation Update 2 August 2023 Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 29 of 2023, sentinel hospitals in the northern provinces reported ILI% of 2.7%, similar to the last week (2.8%), and higher than the same week of 2020-2022 (1.8%, 2.4%, and 2.1%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in northern China, 2020-2023 (Source: China National Influenza Center) Mongolia During week 29 of 2023, the ILI activity in Mongolia decreased to 15 ILI cases per 10,000 population. This is below the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Influenza Situation Update| 3 Bi-weekly Influenza Situation Update 2 August 2023 Republic of Korea In week 29 of 2023, the overall weekly influenza-like illness (ILI) rate was 17.3 per 1,000 outpatient visits, which was similar to the rate recorded in the previous week (16.9) (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korea Disease Control and Prevention Agency). Sentinel influenza surveillance Japan In week 28 of 2023, the number of cases reported weekly by sentinel hospital sites remained low in Japan. The number of cases in 2023 has been consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) IL I ( p er 1 ,0 00 O u tp at ie n t C o n su lt at io n s) Influenza Situation Update| 4 Bi-weekly Influenza Situation Update 2 August 2023 Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed an increase in the overall seasonal influenza activity. In week 29, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 2.3 ILI cases per 1,000 consultations, which was lower than 3.2 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 33.9 ILI cases per 1,000 consultations, which was higher than 24.7 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private medical practitioner clinics, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) China (South) - ILI Surveillance During week 29, the percentage of outpatient or emergency visits for ILI (ILI%) at national sentinel hospitals in southern provinces was 4.4%, lower than the last week (4.5%), higher than the same week in 2020 and 2021 (2.7% and 3.4%), and the same as the corresponding week in 2022 (4.4%) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2023 (Source: China National Influenza Center) Influenza Situation Update| 5 Bi-weekly Influenza Situation Update 2 August 2023 Singapore – Acute Respiratory Infection (ARI) Surveillance In week 29 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,645 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.3%. The overall positivity rate for influenza among ILI samples (n= 919) in the community was 24.7% in the past 4 weeks. Of the 176 specimens tested positive for influenza in Jun 2023, 103 were positive for Influenza A(H3N2) (58.5%), 60 were positive for Influenza A(pH1N1) (34.1%), and 12 were positive for Influenza B (6.8%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 (Source: Singapore Ministry of Health) Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 (Source: Singapore Ministry of Health) Lao PDR During week 29 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of influenza-like illness cases presenting at sentinel sites was 10 cases higher than the previous week. There were 114 samples tested for influenza in week 29, 2023. Influenza A/pdmH1N1 was identified (n=2) (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Influenza Situation Update| 6 Bi-weekly Influenza Situation Update 2 August 2023 Cambodia In week 29 of 2023, the Ministry of Health received data from 7 sentinel sites in Cambodia. During this period, the number of ILI cases in Cambodia decreased between week 28 (202 cases) and week 29 (161 cases) of 2023. In week 28 of 2023, 7 samples tested positive for influenza virus, (Figure 12). The proportion of weekly influenza positive samples fluctuated in 2023. Figure 12: Number of ILI samples from sentinel sites and influenza positivity rate by the week, of 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year-to-date (1 January to 23 July 2023), there have been 174,898 notifications of laboratory- confirmed influenza reported to the National Notifiable Diseases Surveillance System in Australia. There were 22,436 laboratory-confirmed influenza notifications with a diagnosis date this fortnight (Monday 10 July to Sunday 23 July 2023), compared to 33,828 notifications in the previous fortnight. From March 2023, the number of notifications of laboratory-confirmed influenza had gradually increased, but it has significantly decreased after the peak in July. The number of notifications year-to-date is higher than the 5-year average. (Figure 13). Influenza Situation Update| 7 Bi-weekly Influenza Situation Update 2 August 2023 Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2016 to 2023 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) New Zealand – ILI Surveillance In the week ending on 9 July 2023, the influenza-like illness (ILI) general practitioner consultation rates decreased compared to the previous week (17.19 per 100,000 compared to 18.16 per 100,000) (Figure 14). The national rate is lower than that observed at this time in 2022 and the 2015-2019 period. Counties Manukau recorded the highest rate of general practitioner ILI consultations, which is above the national rate and higher than usual for this time of year. Rates in Lakes, Hawke’s Bay, and MidCentral also remain above the national rate. Influenza B and A(H1N1) are the viruses most commonly detected in community surveillance in recent weeks. Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2015-2023 (Source: New Zealand Institute of Environmental Science and Research) Influenza Situation Update| 8 Bi-weekly Influenza Situation Update 2 August 2023 Pacific Island Countries and Areas (PICs) - ILI Surveillance There have been no updates since the previous report. In week 25 of 2023, 18 out of 21 PICs reported ILI surveillance data. 16 out of 18 PICs reported updated data. No reports are available for American Samoa, Guam, and Nauru, and no updates from Federated States of Micronesia and Tuvalu. The following countries reported increased influenza-like illness activity in week 25 compared to the previous week: Republic of the Marshall Islands, Fiji and Vanuatu. (Figure 15). 0 10 20 30 40 50 60 70 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Cook Islands ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 200 400 600 800 1000 1200 1400 1600 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 Fiji ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Baseline 0 100 200 300 400 500 600 700 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 C a se s Epi week French Polynesia ILI trend 2019 - 2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 0 200 400 600 800 1000 1200 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 C a se s Epi week FSM ILI trend 2019 - 2023 (WK 20) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 500 1000 1500 2000 2500 3000 3500 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Kiribati ILI trend 2019-2023 (WK 24) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 50 100 150 200 250 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Marshall Islands ILI trend 2019-2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 Influenza Situation Update| 9 Bi-weekly Influenza Situation Update 2 August 2023 0 20 40 60 80 100 120 140 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s EPi week CNMI ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 ILI 2022 0 100 200 300 400 500 600 700 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week New Caledonia ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 0 20 40 60 80 100 120 140 160 180 200 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Palau ILI Trend 2019 - 2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 5 10 15 20 25 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 C a se s Epi week Niue ILI Trend 2019 - 2023 (WK25) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 1 2 3 4 5 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 C a se s Epi week Pitcairn Islands ILI Trend 2019 - 2023 (WK 25) ILI 2019 ILI 2020 ILI 2021 ILI 2022 ILI 2023 0 500 1000 1500 2000 2500 3000 3500 4000 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Samoa ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 500 1000 1500 2000 2500 3000 3500 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Solomon Islands ILI Trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 0 5 10 15 20 25 30 35 40 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Tokelau ILI Trend 2019 -2023 (WK 24) ILI 2023 ILI 2019 ILI 2020 ILI 2021 Influenza Situation Update| 10 Bi-weekly Influenza Situation Update 2 August 2023 *Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2023-2024 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. Arabic, Chinese, English, French, Russian, Spanish 0 100 200 300 400 500 600 700 800 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C a se s Epi week Tonga ILI trend 2019 -2023 (WK 25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 0 20 40 60 80 100 120 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 Tuvalu ILI trend 2019 -2023 (WK 21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 0 500 1000 1500 2000 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C a se s Epi week Vanuatu ILI Trend 2019 - 2023 (WK25) ILI 2023 ILI 2020 ILI 2021 ILI 2019 0 100 200 300 400 500 600 700 800 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 C a se s Epi week Wallis & Futuna ILI trend 2019 to 2023 (WK25) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022

Bi-weekly Influenza Situation Update 16 August 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 31 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 31 of 2023 have been Influenza A (Figure 1). Caution should be taken when interpreting this data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1 to week 31, 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, week 31, 2022 to week 31, 2023 (Source: WHO FLUNET) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with Country (most recent week of report) Total number of specimens processed Total number of influenza-positive specimens Australia (31 of 2023) 131,949 5,781 Cambodia (30 of 2023) 2,715 369 China (31 of 2023) 783,275 121,306 Fiji (24 of 2023) 2,252 463 Japan (30 of 2023) - 3,006 Lao People’s Democratic Republic (31 of 2023) 3,720 292 Malaysia (31 of 2023) 27,065 5,009 Mongolia (31 of 2023) 10,453 1,532 New Caledonia - - New Zealand (31 of 2023) 1,758 397 Papua New Guinea - - Philippines (30 of 2023) 2,994 279 Republic of Korea (31 of 2023) 9,088 848 Singapore (31 of 2023) 8,245 1,779 Viet Nam (29 of 2023) 769 255 Influenza Situation Update| 2 symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 31 of 2023, sentinel hospitals in the northern provinces reported ILI% of 2.7%, the same as the last week (2.7%), and slightly higher than the same week of 2020-2022 (2.0%, 2.3%, and 2.5%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in northern China, 2020-2023 (Source: China National Influenza Center) Mongolia During week 31 of 2023, the ILI activity in Mongolia decreased to 12 ILI cases per 10,000 population. This is below the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Influenza Situation Update| 3 Republic of Korea In week 31 of 2023, the overall weekly influenza-like illness (ILI) rate was 14.1 per 1,000 outpatient visits, which was slightly lower than the rate recorded in the previous weeks (17.3 on week 29 and 15.0 on week 30) (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korea Disease Control and Prevention Agency). Sentinel influenza surveillance Japan In week 29 of 2023, the number of cases reported weekly by sentinel hospital sites remained low in Japan. The number of cases in 2023 has been consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) IL I ( p er 1 ,0 0 0 O u tp at ie n t C o n su lt at io n s) Influenza Situation Update| 4 Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed a decrease in the overall seasonal influenza activity. In week 31, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 3.0 ILI cases per 1,000 consultations, which was similar to 3.1 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 10.4 ILI cases per 1,000 consultations, which was lower than 29.2 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private medical practitioner clinics, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) China (South) - ILI Surveillance During week 31, the percentage of outpatient or emergency visits for ILI (ILI%) at national sentinel hospitals in southern provinces was 3.9%, lower than the last week (4.3%), higher than the same week in 2020 and 2021 (2.8% and 3.3%), and lower than the corresponding week in 2022 (4.1%) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2023 (Source: China National Influenza Center) Influenza Situation Update| 5 Singapore – Acute Respiratory Infection (ARI) Surveillance In week 31 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,476 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.5%. The overall positivity rate for influenza among ILI samples (n= 1,099) in the community was 27.8% in the past 4 weeks. Of the 297 specimens tested positive for influenza in July 2023, 189 were positive for Influenza A(H3N2) (63.7%), 82 were positive for Influenza A(pH1N1) (27.6%), and one was positive for Influenza A(LVT) (0.3%), and 25 were positive for Influenza B (8.4%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 (Source: Singapore Ministry of Health) Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 (Source: Singapore Ministry of Health) Lao PDR During week 31 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 57 cases lower than the previous week. There were 92 samples tested for influenza in week 31, 2023. Influenza A/pdmH1N1 was identified (n=5) (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Influenza Situation Update| 6 Cambodia There have been no updates since the previous report. In week 29 of 2023, the Ministry of Health received data from 7 sentinel sites in Cambodia. During this period, the number of ILI cases in Cambodia decreased between week 28 (202 cases) and week 29 (161 cases) of 2023. In week 28 of 2023, 7 samples tested positive for influenza virus, (Figure 12). The proportion of weekly influenza positive samples fluctuated in 2023. Figure 12: Number of ILI samples from sentinel sites and influenza positivity rate by the week, of 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year-to-date (1 January to 6 August 2023), there have been 194,790 notifications of laboratory- confirmed influenza reported to the National Notifiable Diseases Surveillance System in Australia. There were 18,098 laboratory-confirmed influenza notifications with a diagnosis date this fortnight (Monday 24 July to Sunday 6 August 2023), compared to 23,016 notifications in the previous fortnight. From March 2023, the number of notifications of laboratory-confirmed influenza had gradually increased, but it has significantly decreased after the peak in July. The number of notifications year-to-date is higher than the 5-year average. (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2016 to 2023 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) Influenza Situation Update| 7 New Zealand – ILI Surveillance In the week ending on 30 July 2023, weekly general practitioner ILI consultation rates decreased compared to the previous week (14.41 per 100,000 compared to 15.63 per 100,000) (Figure 14). The national rate is higher than that observed at this time in 2022 but lower than the 2015-2019 period. Influenza B and A(H1N1) continue to be the most detected viruses in the community in recent weeks. Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2015-2023 (Source: New Zealand Institute of Environmental Science and Research) Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 31 of 2023, 18 out of 21 PICs reported ILI surveillance data. 16 out of 18 PICs reported updated data since week 25. No reports are available for American Samoa, Guam, and Nauru. The following countries reported increased influenza-like illness activity in week 27-31 compared to the previous weeks: Fiji, Palau, Tonga and Vanuatu. (Figure 15). 0 10 20 30 40 50 60 70 1 4 7 101316192225283134374043464952 Cook Islands ILI Trend 2019 -2023 (WK 31) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 200 400 600 800 1000 1200 1400 1600 1 4 7 101316192225283134374043464952 Fiji ILI Trend 2019 -2023 ( WK 27) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Baseline Influenza Situation Update| 8 0 100 200 300 400 500 600 700 1 4 7 101316192225283134374043464952 C a se s Epi week French Polynesia ILI trend 2019 - 2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 0 200 400 600 800 1000 1200 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week FSM ILI trend 2019 - 2023 (WK28) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 500 1000 1500 2000 2500 3000 3500 1 5 9 13 17 21 25 29 33 37 41 45 49 53 C a se s Epi week Kiribati ILI trend 2019-2023 (WK30) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 50 100 150 200 250 1 5 9 13 17 21 25 29 33 37 41 45 49 53 C a se s Epi week Marshall Islands ILI trend 2019 -2023 ( WK 31) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 20 40 60 80 100 120 140 1 4 7 101316192225283134374043464952 C a se s EPi week CNMI ILI Trend 2019 -2023 (WK 30) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 ILI 2022 0 100 200 300 400 500 600 700 1 4 7 101316192225283134374043464952 C a se s Epi week New Caledonia ILI Trend 2019 -2023 (WK 30) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 Influenza Situation Update| 9 0 5 10 15 20 25 1 4 7 101316192225283134374043464952 C a se s Epi week Niue ILI Trend 2019 - 2023 (WK31) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 50 100 150 200 1 5 9 13 17 21 25 29 33 37 41 45 49 53 C a se s Epi week Palau ILI Trend 2019 - 2023 (WK 29) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 1 2 3 4 5 1 4 7 101316192225283134374043464952 C a se s Epi week Pitcairn Islands ILI Trend 2019 - 2023 (WK 31) ILI 2019 ILI 2020 ILI 2021 ILI 2022 ILI 2023 0 500 1000 1500 2000 2500 3000 3500 4000 1 4 7 101316192225283134374043464952 C a se s Epi week Samoa ILI Trend 2019 -2023 ( WK 31) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 500 1000 1500 2000 2500 3000 3500 1 4 7 1 0 1 3 1 6 1 9 2 2 2 5 2 8 3 1 3 4 3 7 4 0 4 3 4 6 4 9 5 2 C a se s Epi week Solomon Islands ILI Trend 2019 -2023 (WK30) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 10 20 30 40 1 4 7 101316192225283134374043464952 C a se s Epi week Tokelau ILI Trend 2019 -2023 (WK 30) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Influenza Situation Update| 10 * Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2023-2024 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. Arabic, Chinese, English, French, Russian, Spanish 0 100 200 300 400 500 600 700 800 1 4 7 1 0 1 3 1 6 1 9 2 2 2 5 2 8 3 1 3 4 3 7 4 0 4 3 4 6 4 9 5 2 C a se s Epi week Tonga ILI trend 2019 -2023 (WK 31) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 20 40 60 80 100 120 1 4 7 101316192225283134374043464952 Tuvalu ILI trend 2019 -2023 (WK 21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 500 1000 1500 2000 1 4 7 1 0 1 3 1 6 1 9 2 2 2 5 2 8 3 1 3 4 3 7 4 0 4 3 4 6 4 9 5 2 C a se s Epi week Vanuatu ILI Trend 2019 - 2023 (WK28) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 200 400 600 800 1 4 7 101316192225283134374043464952 C a se s Epi week Wallis & Futuna ILI trend 2019 - 2023 (WK31) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022

Influenza Situation Update| 1 Bi-weekly Influenza Situation Update 30 August 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 33 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 33 of 2023 have been Influenza A (Figure 1). Caution should be taken when interpreting this data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1 to week 33, 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, week 33, 2022 to week 33, 2023 (Source: WHO FLUNET) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Country (most recent week of report) Total number of specimens processed Total number of influenza-positive specimens Australia (33 of 2023) 139556 6250 Cambodia (31 of 2023) 2880 386 China (33 of 2023) 844846 122980 Fiji (24 of 2023) 2252 463 Japan (32 of 2023) - 3177 Lao People’s Democratic Republic (33 of 2023) 4048 299 Malaysia (33 of 2023) 28892 5438 Mongolia (33 of 2023) 10585 1532 New Caledonia - - New Zealand (33 of 2023) 1923 443 Papua New Guinea - - Philippines (33 of 2023) 3320 297 Republic of Korea (33 of 2023) 9520 868 Singapore (33 of 2023) 8786 1926 Viet Nam (31 of 2023) 815 257 Influenza Situation Update| 2 Bi-weekly Influenza Situation Update 30 August 2023 Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 33 of 2023, sentinel hospitals in the northern provinces reported ILI% of 2.7%, lower than the last week (2.8%), and higher than the same week of 2020-2022 (1.9%, 2.0%, and 2.5%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in northern China, 2020-2023 (Source: China National Influenza Center) Mongolia During week 33 of 2023, the ILI activity in Mongolia decreased to 15 ILI cases per 10,000 population. This is below the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Influenza Situation Update| 3 Bi-weekly Influenza Situation Update 30 August 2023 Republic of Korea In week 33 of 2023, the overall weekly influenza-like illness (ILI) rate was 12.0 per 1,000 outpatient visits, which was lower than the rate recorded in the previous weeks (14.1 on week 31 and 12.5 on week 32) (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korea Disease Control and Prevention Agency). Sentinel influenza surveillance Japan In week 32 of 2023, the number of cases reported weekly by sentinel hospital sites remained low in Japan. The number of cases in 2023 has been consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) IL I ( p er 1 ,0 0 0 O u tp at ie n t C o n su lt at io n s) Influenza Situation Update| 4 Bi-weekly Influenza Situation Update 30 August 2023 Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed an increasein the overall seasonal influenza activity. In week 33, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 4.2 ILI cases per 1,000 consultations, which was higher than 3.8 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 32.8 ILI cases per 1,000 consultations, which was higher than 14.0 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private medical practitioner clinics, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) China (South) - ILI Surveillance During week 33, the percentage of outpatient or emergency visits for ILI (ILI%) at national sentinel hospitals in southern provinces was 4.1%, lower than the last week (4.3%), and higher than the same week in 2020 -2022 (2.7%, 2.8% and 3.3%) (4.1%) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2023 (Source: China National Influenza Center) Influenza Situation Update| 5 Bi-weekly Influenza Situation Update 30 August 2023 Singapore – Acute Respiratory Infection (ARI) Surveillance In week 33 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,377 (over 5.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.5%. The overall positivity rate for influenza among ILI samples (n= 1,124) in the community was 28.2% in the past 4 weeks. Of the 297 specimens tested positive for influenza in July 2023, 189 were positive for Influenza A(H3N2) (63.7%), 82 were positive for Influenza A(pH1N1) (27.6%), and one was positive for Influenza A(LVT) (0.3%), and 25 were positive for Influenza B (8.4%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 (Source: Singapore Ministry of Health) Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 (Source: Singapore Ministry of Health) Lao PDR During week 33 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 72 cases higher than the previous week. There were 115 samples tested for influenza in week 33, 2023. Influenza A/pdmH1N1 (n=1) and Flu A/H3 (n=1) were identified. (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Influenza Situation Update| 6 Bi-weekly Influenza Situation Update 30 August 2023 Cambodia In week 33 of 2023, the Ministry of Health received data from 7 sentinel sites in Cambodia. During this period, the number of ILI cases in Cambodia remains stable between week 32 (183 cases) and week 33 (166 cases) of 2023, and the positivity rate for week 33 is 27.7% (Figure 12). The proportion of weekly influenza positive samples fluctuated in 2023. Figure 12: Number of ILI samples from sentinel sites and influenza positivity rate by the week, of 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year-to-date (1 January to 20 August 2023), there have been 211,491 notifications of laboratory- confirmed influenza reported to the National Notifiable Diseases Surveillance System in Australia. There were 14,287 laboratory-confirmed influenza notifications with a diagnosis date this fortnight (Monday 7 August to Sunday 20 August 2023), compared to 18,542 notifications in the previous fortnight. From March 2023, the number of notifications of laboratory-confirmed influenza had gradually increased, but it has significantly decreased after the peak in July. The number of notifications year-to-date is lower than the 5-year average. (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2016 to 2023 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) Influenza Situation Update| 7 Bi-weekly Influenza Situation Update 30 August 2023 New Zealand – ILI Surveillance In the week ending on 20 August 2023, weekly general practitioner ILI consultation rates decreased slightly compared to the previous week (14.93 per 100,000 compared to 14.97 per 100,000) (Figure 14). The national rate is higher than that observed at this time in 2022 but lower than the 2015-2019 period. Influenza B and A(H1N1) continue to be the most detected viruses in the community in recent weeks. Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2015-2023 (Source: New Zealand Institute of Environmental Science and Research) Pacific Island Countries and Areas (PICs) - ILI Surveillance There have been no updates since the previous report. In week 31 of 2023, 18 out of 21 PICs reported ILI surveillance data. 16 out of 18 PICs reported updated data since week 25. No reports are available for American Samoa, Guam, and Nauru. The following countries reported increased influenza-like illness activity in week 27-31 compared to the previous weeks: Fiji, Palau, Tonga and Vanuatu. (Figure 15). 0 10 20 30 40 50 60 70 1 4 7 101316192225283134374043464952 Cook Islands ILI Trend 2019 -2023 (WK 31) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 200 400 600 800 1000 1200 1400 1600 1 4 7 101316192225283134374043464952 Fiji ILI Trend 2019 -2023 ( WK 27) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Baseline Influenza Situation Update| 8 Bi-weekly Influenza Situation Update 30 August 2023 0 100 200 300 400 500 600 700 1 4 7 101316192225283134374043464952 C a se s Epi week French Polynesia ILI trend 2019 - 2023 (WK 25) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 0 200 400 600 800 1000 1200 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week FSM ILI trend 2019 - 2023 (WK28) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 500 1000 1500 2000 2500 3000 3500 1 5 9 13 17 21 25 29 33 37 41 45 49 53 C a se s Epi week Kiribati ILI trend 2019-2023 (WK30) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 50 100 150 200 250 1 5 9 13 17 21 25 29 33 37 41 45 49 53 C a se s Epi week Marshall Islands ILI trend 2019 -2023 ( WK 31) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 20 40 60 80 100 120 140 1 4 7 101316192225283134374043464952 C a se s EPi week CNMI ILI Trend 2019 -2023 (WK 30) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 ILI 2022 0 100 200 300 400 500 600 700 1 4 7 101316192225283134374043464952 C a se s Epi week New Caledonia ILI Trend 2019 -2023 (WK 30) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 Influenza Situation Update| 9 Bi-weekly Influenza Situation Update 30 August 2023 0 5 10 15 20 25 1 4 7 101316192225283134374043464952 C a se s Epi week Niue ILI Trend 2019 - 2023 (WK31) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 50 100 150 200 1 5 9 13 17 21 25 29 33 37 41 45 49 53 C a se s Epi week Palau ILI Trend 2019 - 2023 (WK 29) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 1 2 3 4 5 1 4 7 101316192225283134374043464952 C a se s Epi week Pitcairn Islands ILI Trend 2019 - 2023 (WK 31) ILI 2019 ILI 2020 ILI 2021 ILI 2022 ILI 2023 0 500 1000 1500 2000 2500 3000 3500 4000 1 4 7 101316192225283134374043464952 C a se s Epi week Samoa ILI Trend 2019 -2023 ( WK 31) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 500 1000 1500 2000 2500 3000 3500 1 4 7 1 0 1 3 1 6 1 9 2 2 2 5 2 8 3 1 3 4 3 7 4 0 4 3 4 6 4 9 5 2 C a se s Epi week Solomon Islands ILI Trend 2019 -2023 (WK30) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 10 20 30 40 1 4 7 101316192225283134374043464952 C a se s Epi week Tokelau ILI Trend 2019 -2023 (WK 30) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Influenza Situation Update| 10 Bi-weekly Influenza Situation Update 30 August 2023 * Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: • New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link • Recommended composition of influenza virus vaccines for use in the 2023-2024 northern hemisphere influenza season Link • WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link • WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. Arabic, Chinese, English, French, Russian, Spanish 0 100 200 300 400 500 600 700 800 1 4 7 1 0 1 3 1 6 1 9 2 2 2 5 2 8 3 1 3 4 3 7 4 0 4 3 4 6 4 9 5 2 C a se s Epi week Tonga ILI trend 2019 -2023 (WK 31) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 20 40 60 80 100 120 1 4 7 101316192225283134374043464952 Tuvalu ILI trend 2019 -2023 (WK 21) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 500 1000 1500 2000 1 4 7 1 0 1 3 1 6 1 9 2 2 2 5 2 8 3 1 3 4 3 7 4 0 4 3 4 6 4 9 5 2 C a se s Epi week Vanuatu ILI Trend 2019 - 2023 (WK28) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 200 400 600 800 1 4 7 101316192225283134374043464952 C a se s Epi week Wallis & Futuna ILI trend 2019 - 2023 (WK31) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022

Bi-weekly Influenza Situation Update 13 September 2023 Virological Surveillance Summary The total number of specimens and number of positive specimens reported to FluNet by Western Pacific Region countries and areas between week 1 and week 35 of 2023 are presented in Table 1 below. Influenza A and B are co-circulating, however, the majority of cases reported to week 35 of 2023 have been Influenza A (Figure 1). Caution should be taken when interpreting this data as there are reporting delays. Table 1: Cumulative data reported to FluNet from Western Pacific Region, week 1 to week 35, 2023 Figure 1: Number of specimens positive for influenza by subtype, Western Pacific Region, week 35, 2022 to week 35, 2023 (Source: WHO FLUNET) Influenza surveillance summary Influenza surveillance in the WHO Western Pacific Region is based on outpatient and inpatient indicator- based surveillance (IBS) systems, as well as event-based surveillance. Case definitions, population groups included and data formats differ among countries. This influenza surveillance summary includes countries and areas where routine IBS is conducted and information is available. The WHO surveillance case definition for influenza-like illness (ILI) is an acute respiratory infection with a measured fever of ≥38oC and cough, with symptom onset within the last 10 days. For SARI, it is an acute respiratory infection (ARI) with a history of fever or measured fever of ≥38oC and cough, with symptom onset within 10 days that requires hospitalization. Sentinel site data should be interpreted with caution since the number of sites reporting may vary between weeks Country (most recent week of report) Total number of specimens processed Total number of influenza-positive specimens Australia (35 of 2023) 192503 12688 Cambodia (35 of 2023) 3440 423 China (35 of 2023) 910767 124974 Fiji (24 of 2023) 2252 463 Japan (34 of 2023) 3252 Lao People’s Democratic Republic (35 of 2023) 4431 316 Malaysia (35 of 2023) 30653 5831 Mongolia (33 of 2023) 10585 1532 New Caledonia - - New Zealand (35 of 2023) 2117 490 Papua New Guinea - - Philippines (33 of 2023) 3320 297 Republic of Korea (35 of 2023) 10136 887 Singapore (35 of 2023) 9351 2068 Viet Nam (33 of 2023) 881 257 Influenza Situation Update| 2 Countries in the temperate zone of the Northern Hemisphere In countries within the temperate zone of the Northern Hemisphere, ILI and influenza activity are similar to the corresponding period from previous years. Outpatient ILI Surveillance China (North) During week 35 of 2023, sentinel hospitals in the northern provinces reported ILI% of 2.8% was similar compared to higher than the last week (2.7%), and higher than the same week of 2020-2022 (1.8%, 1.7%, and 2.5%) (Figure 2). Figure 2: Percentage of visits for ILI at sentinel hospitals in northern China, 2020-2023 (Source: China National Influenza Center) Mongolia During week 34 of 2023, the ILI activity in Mongolia increased to 16 ILI cases per 10,000 population. This is below the upper tolerance limit (Figure 3). Figure 3: Proportion of outpatient ILI visits per 10,000 people in Mongolia, 2020-2023 (Source: Mongolia National Influenza Center) Influenza Situation Update| 3 Republic of Korea In week 34 of 2023, the overall weekly influenza-like illness (ILI) rate was 10.6 per 1,000 outpatient visits, which was lower than the rate recorded in the previous weeks (12.0 on week 33 and 12.5 on week 32) (Figure 4). Figure 4: Weekly ILI incidence rate per 1,000 outpatient consultations, Republic of Korea, 2018-2023 (Source: Korea Disease Control and Prevention Agency). Sentinel influenza surveillance Japan In week 34 of 2023, the number of cases reported weekly by sentinel hospital sites remained low in Japan. The number of cases in 2023 has been consistently low (Figure 5). Figure 5: Number of influenza cases reported weekly per reporting sentinel hospital site, Japan 2013-2023 (Source: Japan National Institute of Infectious Diseases) Influenza Situation Update| 4 Countries/areas in the tropical zone ILI and influenza activity is similar to the corresponding period from previous years in some of the countries and areas in the tropical zone. Hong Kong SAR (China) – ILI and hospital Surveillance The latest surveillance data showed an increasein the overall seasonal influenza activity. In week 35, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPC) was 7.4 ILI cases per 1,000 consultations, which was higher than 5.6 recorded in the previous week (Figure 6). The average consultation rate for ILI among sentinel private medical practitioner (PMP) clinics was 42.1 ILI cases per 1,000 consultations, which was lower than 56.5 recorded in the previous week (Figure 7). Figure 6: ILI consultation rates at sentinel general outpatient clinics, Hong Kong SAR 2020-2023 Figure 7: ILI consultation rates at sentinel private medical practitioner clinics, Hong Kong SAR 2019-2023 (Source: Hong Kong Centre for Health Protection) (Source: Hong Kong Centre for Health Protection) China (South) - ILI Surveillance During week 35, the percentage of outpatient or emergency visits for ILI (ILI%) at national sentinel hospitals in southern provinces was 3.9%, similar compared to lower than the last week (4.0%), and higher than the same week in 2020 -2022 (2.7%, 2.7% and 2.9%) (Figure 8). Figure 8: Percentage of visits due to ILI at national sentinel hospitals in Southern China, 2019-2023 (Source: China National Influenza Center) Influenza Situation Update| 5 Singapore – Acute Respiratory Infection (ARI) Surveillance In week 35 of 2023, the average daily number of patients seeking treatment in the polyclinics for ARI is 2,426 (over 4.5 working days) (Figure 9). The proportion of patients with influenza-like illness (ILI) among the polyclinic attendances for ARI is 0.4%. The overall positivity rate for influenza among ILI samples (n= 1,106) in the community was 26.1% in the past 4 weeks. Of the 351 specimens tested positive for influenza in August 2023, 241 were positive for Influenza A(H3N2) (69%), 87 were positive for Influenza A(pH1N1) (25%), and 23 were positive for Influenza B (6%) (Figure 10). Figure 9: Average daily polyclinic attendances for ARI in Singapore, 2022-2023 (Source: Singapore Ministry of Health) Figure 10: Monthly influenza surveillance for ARI in Singapore, 2018-2023 (Source: Singapore Ministry of Health) Lao PDR During week 35 of 2023, the National Center for Laboratory and Epidemiology received data from all seven sentinel sites in Lao PDR. The number of ILI cases presenting at sentinel sites was 16 cases higher than the previous week. There were 105 samples tested for influenza in week 35, 2023. Influenza A/pdmH1N1 (n=4) and Flu A/H3 (n=1) were identified. (Figure 11). Figure 11: Weekly number of ILI cases at sentinel sites (2019 to 2023) (Source: Lao National Center for Laboratory and Epidemiology) Influenza Situation Update| 6 Cambodia In week 35 of 2023, the Ministry of Health received data from 7 sentinel sites in Cambodia. During this period, the number of ILI cases in Cambodia increased slightly in week 35 compared to week 34 (162 cases), and the positivity rate for week 35 is 0% (Figure 12). The proportion of weekly influenza positive samples fluctuated in 2023. Figure 12: Number of ILI samples from sentinel sites and influenza positivity rate by the week, of 2020-2023, Cambodia (Source: Communicable Disease Control Department, Cambodia Ministry of Health) Countries in the temperate zone of the southern hemisphere In the temperate zone of the southern hemisphere, influenza activity is reported during the influenza season, usually starting in May in Australia and New Zealand. Australia – Laboratory-confirmed influenza In the year-to-date (1 January to 3 September 2023), there have been 224,873 notifications of laboratory-confirmed influenza reported to the National Notifiable Diseases Surveillance System in Australia. There were 12,082 laboratory-confirmed influenza notifications with a diagnosis date this fortnight (Monday 21 August to Sunday 3 September 2023), compared to 14,535 notifications in the previous fortnight. From March 2023, the number of notifications of laboratory-confirmed influenza had gradually increased, but it has significantly decreased after the peak in July. The number of notifications year-to-date is lower than the 5-year average. (Figure 13). Figure 13: Notifications of laboratory-confirmed influenza by month and week from 2016 to 2023 in Australia (Source: National Notifiable Diseases Surveillance System, Australian Department of Health) Influenza Situation Update| 7 New Zealand – ILI Surveillance In the week ending on 3 September 2023, weekly general practitioner ILI consultation rates decreased slightly compared to the previous week (32.88 per 100,000 compared to 33.09 per 100,000) (Figure 14). The national rate is higher than that observed at this time in 2022 but lower than the 2015-2019 period. Influenza B and A(H1N1) continue to be the most detected viruses in the community in recent weeks. Figure 14: Weekly rates of general practice ILI consultations per 100,000 people in New Zealand in 2015-2023 (Source: New Zealand Institute of Environmental Science and Research) Pacific Island Countries and Areas (PICs) - ILI Surveillance In week 36 of 2023, 18 out of 21 PICs reported ILI surveillance data. Most PICs reported updated data since week 35. No reports are available for American Samoa, Guam, and Nauru. The following countries reported increased influenza-like illness activity in week 33-36 compared to the previous weeks: Commonwealth of Northern Mariana Islands, Fiji and French Polynesia. (Figure 15). 0 10 20 30 40 50 60 70 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi Week Cook Islands ILI Trend 2019 -2023 (WK 36) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 300 600 900 1200 1500 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi Week Fiji ILI Trend 2019 -2023 (WK 36) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Baseline Influenza Situation Update| 8 0 100 200 300 400 500 600 700 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C a se s Epi week French Polynesia ILI trend 2019 - 2023 (WK 35) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 0 100 200 300 400 500 600 700 800 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C a se s Epi week FSM ILI trend 2019 - 2023 (WK35) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 500 1000 1500 2000 2500 3000 3500 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Kiribati ILI trend 2019-2023 (WK35) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 50 100 150 200 250 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Marshall Islands ILI trend 2019 -2023 (WK 35) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 20 40 60 80 100 120 140 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s EPi week CNMI ILI Trend 2019 -2023 (WK 35) ILI 2023 ILI 2020 ILI 2021 ILI 2022 ILI 2019 ILI 2022 0 100 200 300 400 500 600 700 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week New Caledonia ILI Trend 2019 -2023 (WK 34) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 Influenza Situation Update| 9 0 5 10 15 20 25 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Niue ILI Trend 2019 - 2023 (WK36) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 20 40 60 80 100 120 140 160 180 200 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Palau ILI Trend 2019 - 2023 (WK 36) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 0 1 2 3 4 5 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Pitcairn Islands ILI Trend 2019 - 2023 (WK 31) ILI 2019 ILI 2020 ILI 2021 ILI 2022 ILI 2023 0 500 1000 1500 2000 2500 3000 3500 4000 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Samoa ILI Trend 2019 -2023 (WK 36) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 500 1000 1500 2000 2500 3000 3500 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C a se s Epi week Solomon Islands ILI Trend 2019 -2023 (WK35) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 5 10 15 20 25 30 35 40 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Tokelau ILI Trend 2019 -2023 (WK 29) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 Baseline Influenza Situation Update| 10 * Caution should be taken in interpreting these data as there may be changes in the number of sentinel sites reporting to the Pacific Syndromic Surveillance System. ** FSM: Federated States of Micronesia, CMNI: Commonwealth of Northern Mariana Islands Figure 15: Reported cases of influenza-like illness in Pacific Island Countries, 2019-2023 (Source: Pacific Syndromic Surveillance System Weekly Bulletin) Global influenza situation updates Virological update Global update Others: New recommended composition of influenza virus vaccines for use in the 2023 southern hemisphere influenza season Link Recommended composition of influenza virus vaccines for use in the 2023-2024 northern hemisphere influenza season Link WHO Consultation on the Composition of Influenza Virus Vaccines for Use in the 2023 Southern Hemisphere Influenza Season 19-22 September 2022 Link WHO issues updated influenza vaccines position paper Link WHO's YouTube Channel: film exploring a number of key aspects of the constant evolution of influenza viruses and associated impacts on public health. Arabic, Chinese, English, French, Russian, Spanish 0 100 200 300 400 500 600 700 800 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Tonga ILI trend 2019 -2023 (WK 35) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 20 40 60 80 100 120 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi Week Tuvalu ILI trend 2019 -2022 (WK 26) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022 0 500 1000 1500 2000 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C a se s Epi week Vanuatu ILI Trend 2019 - 2023 (WK30) ILI 2023 ILI 2020 ILI 2021 ILI 2019 ILI 2022 -100 100 300 500 700 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 C as e s Epi week Wallis & Futuna ILI trend 2019 to 2023 (WK35) ILI 2023 ILI 2019 ILI 2020 ILI 2021 ILI 2022