Influenza virus characterization: summary report, Europe, January 2024

EE Influenza virus characterization Summary report, Europe, January 2024 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Document number: WHO/EURO:2024‑6189‑45954‑73244 ©World Health Organization and the European Centre for Disease Prevention and Control 2024 Somerights reserved. Thiswork is availableunder theCreativeCommonsAttribution‑ 3.0 IGO licence (CCBY‑3.0 IGO; Creative Commons — Attribution 3.0 IGO— CC BY 3.0 IGO). Under the terms of this licence, you may copy, redistribute and adapt the work, even commercially, provided the work is appropriately cited, as indicated below. In any use of this work, there should be no suggestion that WHO or ECDC endorse any specific organization, products or services. The use of the WHO or ECDC logo is not permitted. If you adapt the work, then you must license your work under the same or equivalent Creative Commons licence. If you create a translation of this work, you should add the following disclaimer along with the suggested citation: “This translation was not created by the World Health Organization (WHO) or the European Centre for Disease Prevention and Control (ECDC). WHO and ECDC are not responsible for the content or accuracy of this translation. The original English edition shall be the binding and authentic edition: Influenza virus characterization: summary report, Europe, January 2024. Copenhagen: WHO Regional Office for Europe and Stockholm: European Centre for Disease Prevention and Control; 2024”. Suggested citation. Influenza virus characterization: summary report, Europe, January 2024. Copenhagen: WHO Regional Office for Europe and Stockholm: European Centre for Disease Prevention and Control; 2024. Licence: CC BY 3.0 IGO. Cataloguing‑in‑Publication (CIP) data. CIP data are available at http://apps.who.int/iris. Sales, rights and licensing. To purchase WHO publications, see http://apps.who.int/bookorders. To submit requests for commercial use and queries on rights and licensing, see http://www.who.int/about/licensing. Third‑party materials. If you wish to reuse material from this work that is attributed to a third party, such as tables, figures or images, it is your responsibility to determine whether permission is needed for that reuse and to obtain permission from the copyright holder. The risk of claims resulting from infringement of any third‑ party‑owned component in the work rests solely with the user. The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the World Health Organization and ECDC concerning the legal status of any country, territory, area or city or of its authorities, or concerning the delimitation of its frontiers or boundaries. Dotted lines onmaps represent approximate border lines for which there may not yet be full agreement. Thementionof specific companiesor of certainmanufacturers’ productsdoesnot imply that theyareendorsed or recommended by the World Health Organization and ECDC in preference to others of a similar nature that are not mentioned. Errors and omissions excepted, the names of proprietary products are distinguished by initial capital letters. All reasonable precautions have been taken by the World Health Organization and ECDC to verify the information contained in this publication. However, the published material is being distributed without warranty of any kind, either expressed or implied. The responsibility for the interpretation and use of the material lies with the reader. In no event shall the World Health Organization and ECDC be liable for damages arising from its use. This publication follows WHO institutional style guidelines which reflects the WHO Style Guide with regard to names and designation of countries, territories, areas or cities, or of their authorities. The names and designations of countries, territories, areas and cities used in this publication should not be understood as an endorsement by ECDC of the terminology used. 2 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Contents Acknowledgements 4 Summary of the latest WHO Influenza Vaccine Compositionmeetings 5 Influenza by type/subtype 6 Worldwide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 European region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Summary of influenza detections in the WHO European Region, week 35/2023 to 3/2024 8 Sentinel surveillance system dynamics, week 35/2023 to 49/2023 9 Genetic diversity by Type/Lineage and group 10 Influenza A/H1N1 11 Genetic analyses: A/H1N1 11 Maximum likelihood phylogenetic trees: A/H1N1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Summary of the antigenic properties of A/H1N1 viruses circulating in the reporting period 13 A/H1N1: References 13 Influenza A/H3N2 14 Genetic analyses: A/H3N2 14 Maximum likelihood phylogenetic tree: A/H3N2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Summary of the antigenic properties of A/H3N2 viruses circulating in the reporting period 16 A/H3N2: HI reagents and references 16 Influenza B 17 Genetic analyses: B/Victoria 17 Maximum likelihood phylogenetic tree: B/Victoria . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Summary of the antigenic properties of B/Victoria lineage viruses circulating in the reporting period 19 B/Victoria: Reagents and references 19 Antiviral susceptibility testing 20 Summaries of data submitted to TESSy 20 Genetic characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 (According to the guidance produced for TESSy reporting at the beginning of the 2023‑2024 influenza season) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Susceptibility to antivirals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Annex 21 A/H1N1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 A/H3N2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 B/Victoria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 WHO Collaborating Centre reports 23 3 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Acknowledgements This report was prepared by the Worldwide Influenza Centre, Francis Crick Institute (WIC), with contributions from: Prof. Nicola Lewis (Director) Dr Ruth Harvey (Deputy Director) Dr Monica Galiano (Head of Molecular Testing and Genomics) Dr Zheng Xiang Ms Becky Clark Ms Alice Lilley Ms Christine Carr Mr Michael Bennett Dr Tanya Mikaiel Ms Abi Lofts Dr Alize Proust Ms Chandrika Halai Dr Karen Cross Ms Aine Rattigan Mr Lorin Adams for the World Health Organization Regional Office for Europe under WHO contract. Data from The European Surveillance System – TESSy was provided by the respective country and area and released by ECDC. We thank all those who have contributed information, clinical specimens and viruses, and associated data to the WHO Global Influenza Surveillance and Response System (GISRS), which provides the basis for our current understanding of recently circulating influenza viruses included in this summary. This report was prepared in part using data reported to the European Surveillance System (TESSy). We gratefully acknowledge the authors, originating and submitting laboratories of the sequences from the GISAID EpiFluTM database, which were downloaded for use in the preparation of this report (all submitters of data may be contacted directly via the GISAID website), along with all laboratories who submitted sequences directly to WHO CC London. 4 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Summary of the latest WHO Influenza Vaccine Compositionmeetings Genetic and antigenic characterization data generated at the Worldwide Influenza Centre for viruses with collection dates after 31 January 2023 until 31 August 2023 informed the WHO influenza vaccine composition meeting (VCM) in September 2023 when recommendations were made for the southern hemisphere (SH) 2024 influenza season. At the September 2023 VCM it was recommended to change the A(H1N1)pdm09 and A(H3N2) vaccine components for the 2024 SH season. Previously, at the February 2023 VCM, which focused on data from viruses collected after 31 August 2022 until 31 January 2023, it was also recommended to change the A(H1N1)pdm09 vaccine component for the 2023‑2024 northern hemisphere (NH) season. It is recommended vaccines for use in the 2024 SH influenza season contain the following: Trivalent: Egg‑based Vaccines • an A/Victoria/4897/2022 (H1N1)pdm09‑like virus; • an A/Thailand/8/2022 (H3N2)‑like virus; and • a B/Austria/1359417/2021 (B/Victoria lineage)‑like virus. Trivalent: Cell‑ or recombinant‑based Vaccines • an A/Wisconsin/67/2022 (H1N1)pdm09‑like virus; • an A/Massachusetts/18/2022 (H3N2)‑like virus; and • a B/Austria/1359417/2021 (B/Victoria lineage)‑like virus. Quadrivalent (egg‑ or cell culture‑ or recombinant‑based vaccines): Above 3 components; and a B/Phuket/3073/2013 (B/Yamagata lineage)‑like virus. Influenza B/Yamagata‑lineage No B/Yamagata‑lineage viruses with collection dates after March 2020 have been detected or sequences released in GISAID as of 23rd January 2024. The absence of confirmed detection of naturally occurring B/Yamagata lineage viruses is indicative of very low risk of infection by B/Yamagata lineage viruses. Therefore, it is the opinion of the WHO influenza vaccine composition advisory committee that inclusion of a B/Yamagata lineage antigen in quadrivalent influenza vaccines is no longer warranted, and every effort should be made to exclude this component as soon as possible. A continued effort by all NICs of GISRS is required to identify B/Yamagata‑lineage viruses for detailed characterization to determine if there are any in circulation. 5 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Influenza by type/subtype Worldwide Geographical distribution of influenza viruses with collection dates from 1st September 2023 through to 23rd January 2024 as deposited in GISAID, coloured by Type/subtype. Geographic markers scaled to detection proportions. Full length HA. Map provided by WHO GIS Centre for Health, DNA/DDI. Timeline obtained with Microreact Globally, influenza detections remain elevated since the last report in December 2023. The relative proportions of A/H1N1, A/H3N2 and B/Victoria varied by geographic region with with cocirculation of A/H1N1 and A/H3N2 overall and some predominance of B/Victoria mostly in South America and South Africa, as indicated by the different colours in the pie charts by country. 6 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 European region Geographical distribution in the European region of influenza viruses with collection dates from 1st September 2023 through to 23rd January 2024 as deposited in GISAID, coloured by Type/subtype. Geographic markers scaled to detection proportions. Full length HA.Map provided by WHO GIS Centre for Health, DNA/DDI.Timeline obtained with Microreact In the European region, influenza detections have increased since the last report in December 2023 and remained elevated for the past 4 weeks. The majority of countries which reported detections showed co‑circulation of A/H1N1 and A/H3N2 and sporadic detections of influenza B/Victoria, as indicated by the different colours in the pie charts. 7 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Summary of influenza detections in the WHO European Region, week 35/2023 to 3/2024 Table 1 shows influenza virus detections in the WHO European Region reported to The European Surveillance System (TESSy) database from 1st September 2023 (weeks 35/2023 to 3/2024) compared with the same period in the previous season. For type‑percentage calculations, the denominator is total detections; for subtype and lineage, it is the total influenza A subtyped and total influenza B lineage determined, respectively. As not all countries have a true non‑sentinel testing denominator, no percentage calculations for total tested are shown (Data taken from Flu News Europe reports and from ERVISS (European Respiratory Virus Surveillance Summary)). Cumulative number of detections for weeks 35/2023 to 3/2024 Cumulative number of detections for weeks 35/2022 to 3/2023 Virus type/subtype/lineage Sentinel sources Non‑sentinel sources Totals % Sentinel sources Non‑sentinel sources Totals % Influenza A 6546 78347 84893 98 7399 84649 92048 91 A(H1N1)pdm09 4117 13384 17501 76 1528 15206 16734 57 A(H3N2) 1127 4384 5511 24 3870 8738 12608 43 A not subtyped 1302 60579 61881 NA 2001 60705 62706 NA Influenza B 113 1585 1698 2 816 8511 9327 9 Victoria lineage 0 220 220 100 226 221 447 100 Yamagata lineage 0 0 0 NA 0 0 0 NA Lineage not ascribed 113 1365 1478 NA 590 8290 8880 NA Total detections 6659 79932 86591 NA 8215 93160 101375 NA Total tested 51424 901210 952634 NA 45904 926809 972713 NA Compared with the same period (weeks 35 to 3) in 2022‑2023, for sentinel surveillance the number of specimens tested is slightly higher, whereas the number of influenza detections has slightly decreased. For non‑sentinel surveillance, the number of tested specimens has decreased from last season to the current, as well as the number of detections. In both periods, the proportion of influenza A of unknown subtype was around 20% of sentinel cases and 70% of non‑sentinel cases of the total influenza A detected. Relative frequencies of type A vs B influenza viruses continue to show predominance of influenza A with a proportion of 98% compared with 91% in 2022‑2023. Currently, in Europe there are sporadic detections of influenza B (2%), with most of the global detections circumscribed to the Americas. Relative frequencies of influenza A subtypes have also shifted, with A/H1N1 viruses increasing from 48% to 76% frequency, and a higher proportion of circulating A/H1N1 viruses (76% A/H1N1 vs 24% A/H3N2) compared to last season (57% A/H1N1 vs 43% A/H3N2). 8 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Sentinel surveillance system dynamics, week 35/2023 to 49/2023 Figure adapted from ERVISS During the period from week 35/2023 to week 3 of 2024, influenza activity remained at low levels through the reporting period until week 46 when it started to increase, crossing the epidemic threshold of 10% in week 50. This marks a late start of the influenza season when compared with the previous season where the epidemic threshold of 10% had been crossed by week 45. Across sentinel surveillance, influenza A/H3N2 and A/H1N1 viruses cocirculatedwith predominance of A/H1N1 during most of this period, with overall frequencies of 78% for A/H1N1 and 22% for A/H3N2. 9 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Genetic diversity by Type/Lineage and group 10 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Influenza A/H1N1 Genetic analyses: A/H1N1 6B.1A.5a.2a and 6B.1A.5a.2a.1 clade viruses both continued to circulate with differing relative proportions depending on region, with a global predominance of 5a.2a viruses. In Europe, both 5a.2a and 5a.2a.1 viruses were detected, with 5a.2a predominating in 2/3 of A/H1N1 sequenced viruses. Within the 5a.2a viruses, characterised by substitutions K54Q, A186T, E224A, R259K and K308R, some heterogeneity was observed: a recently emerged minor subclade with D94N and T216A (C.1.7, no reference assigned yet), with viruses predominating in Australia, New Zealand and Indonesia, and in minor proportions in Europe and Asia; a large subclade defined by substitution I418V (A/Sydney/5/2021, subclade C.1) which was predominating in the Middle East, Africa, South‑East Asia, Central America and some countries in Europe, and circulated in significant proportions in other countries; this subclade included a cluster characterised by T120A with K169Q or V47I and another with P137S. Other subclades that were reported in previous weeks were not seen during this period, except for one with A48P (A/Maine/10/2022, subclade C.1.2) with viruses from Thailand and Vietnam. Within the 5a.2a.1 viruses, characterised by substitutions P137S, K142R, D260E, T277A, E356D and N451H, there are twomain groups of viruses: a major clade with T216A (A/Victoria/4897/2022, C.1.1.1) predominating in the US, the Caribbean, Japan and some countries in Europe, showing additional heterogeneity with a cluster with R45K; and a minor clade represented by A/Wisconsin/67/2022 (C.1.1) circulating in Brazil, Europe and South East Asia. Global geographical distribution of influenza A/H1N1 genetic clades (subclades) viruses, obtained with full HA sequences as deposited in GISAID and classified using Nextclade.Geographic markers scaled to detection proportions. Map provided by WHO GIS Centre for Health, DNA/DDI Maximum likelihood phylogenetic trees: A/H1N1 Maximum likelihood phylogenetic tree inferred using Iqtree2 from HA sequence data obtained from GISAID from 1st September onwards. Trees were manually curated and, if sequence numbers were > 200, downsampled using Treemer to retain a representative tree topology of 200 sequences with emphasis on viruses from the European region. Annotation of amino acids substitutions was performed with Treetime ancestral reconstruction. References and CVVs are marked as Cell or Egg. 11 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 12 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Summaryof theantigenicpropertiesofA/H1N1viruses circulating in the reporting period Both cell‑ and egg‑based NH 2023‑24 strain A/Victoria/4897/2022 recognises both 5a.2a and 5a.2a.1 test viruses well. For an overall picture of the past season, see the Annex. A/H1N1: References Virus Genetic group Virus passage Ferret ID IVR‑215 (A/Victoria/2570/2019) 5a.2 E4/D7/E3 F37/21 A/Sydney/5/2021 5a.2a MDCK3/MDCK3 F46/22 A/Sydney/5/2021 5a.2a E3/E3 F04/22 A/Victoria/4897/2022 5a.2a.1 SIAT2/MDCK2 F05/23 IVR‑238 (A/Victoria/4897/2022) 5a.2a.1 E3/D6/E1 F07/23 A/Wisconsin/67/2022 5a.2a.1 MDCK2 F17/23 13 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Influenza A/H3N2 Genetic analyses: A/H3N2 Clade 3C.2a1b.2a.2 (renamed as 2 since February 2023) predominated since 1st February in all geographic regions where A/H3N2 circulated. During this reporting period, the great majority of H3 viruses detected belong to clade 2a.3a.1, which share substitution E50K with clade 2a.3a and present additional substitutions I140K and I223V (A/Thailand/8/2022, subclade H). Within clade 2a.3a.1, viruses with I25V, V347M and some with I418V (subclade H.1) represented by new reference A/Sydney/856/2023 were seen in Europe, South‑East Asia and Australia, whereas viruses with N122D and K276E (subclade H.2) represented by new reference A/Sydney/878/2023 were predominating in Europe, the US and the Middle East. Clade 2a.3a.1 included a subclade with N122D and V347M viruses from US, Australia and Qatar (the latter characterised by V112I and S145N) whereas the rest of clade 2a.3a.1 was detected in Africa, South East Asia and a minority in Europe and the US, with no subclade‑specific amino acids. Minor subclade H.4 (no reference assigned yet) was seen in Norway, West Africa and Central America. A few viruses predominating in West Africa with substitutions K276E and V347M form a cluster within clade 2a.3a (A/Finland/402/2023). Global geographical distribution of influenza A/H3N2 genetic clades (subclades) viruses, obtained with full HA sequences as deposited in GISAID and classified using Nextclade.Geographic markers scaled to detection proportions. Map provided by WHO GIS Centre for Health, DNA/DDI Maximum likelihood phylogenetic tree: A/H3N2 Maximum likelihood phylogenetic tree inferred using Iqtree2 from HA sequence data obtained from GISAID from 1st September onwards. Trees were manually curated and, if sequence numbers were > 200, downsampled using Treemer to retain a representative tree topology of 200 sequences with emphasis on viruses from the European region. Annotation of amino acids substitutions was performed with Treetime ancestral reconstruction. References and CVVs are marked as Cell or Egg. 14 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 15 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Summaryof theantigenicpropertiesofA/H3N2viruses circulating in the reporting period We note variable recognition by current 2a.3a.1 reference and vaccine antisera for a number of 2a.3a.1 viruses that have been analysed since September. For an overall picture of the past season, see the Annex. A/H3N2: HI reagents and references Virus Genetic group Virus passage Ferret ID A/Thuringen/10/2022 2b P1/SIAT2 F36/22 A/Stockholm/5/2021 2a SIAT0/SIAT3 F35/21 A/Darwin/9/2021 2a E3/E4 F39/21 A/Norway/24873/2021 2a.3 SIAT2 F10/22 A/Norway/24873/2021 2a.3 E3 (Am2Al1) F11/22 A/Poland/97/2022 2a.2 S2 F39/22 A/Slovenia/8720/2022 2a.1 SIAT1/MDCK1/SIAT2 F24/22 A/Lille/50053/2022 2a.1 MDCK1/SIAT3 F02/23 A/Catalonia/NSVH161512067/2022 2a.1b SIAT1/SIAT3 F41/22 A/Albania/289813/2022 2a.3a.1 MDCK1 F21/23 A/Brandenburg/15/2022 2a.3a.1 E5(Am1AI2) F18/23 A/Switzerland/28719/2022 2b SIAT1 F29/23 A/Massachusetts/18/2022 2a.3a.1 SIAT3/SIAT1 F36/23 A/California/122/2022 2a.3a.1 E1/E1 F33/23 A/Thailand/08/2022 2a.3a.1 E3/E1 F34/23 IVR‑237(A/Thailand/08/2022) 2a.3a.1 E3/D7/E1 F35/23 16 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Influenza B Genetic analyses: B/Victoria Clade V1A.3a.2 viruses characterised by substitutions A127T, P144L, N150K, G184E, N197D (‑CHO), K203R and R279K (B/Austria/1359417/2021, subclade C) predominated since 1st February 2023 in geographic regions where B/Victoria‑lineage viruses were detected. During this reporting period, only a minority of B/Victoria viruses were detected and characterised in Europe. Within V1A.3a.2, the most recent viruses are characterised by additional substitution D197E, represented by B/Connecticut/01/2021 (subclade C.5). Subclades observed within V1A.3a.2 (C.5) are: C.5.1 with E183K represented by B/Catalonia/2279261NS/2023, detected in Central America, Brazil, the US and Europe; C.5.4 (B/Slovenia/924/2023) with V117I, E128K, A154T and K326R detected in the Americas; C.5.5 (B/Paraguay/2102/2023) with R80G, E184K detected in US and Central/South America; C.5.6 (B/Norway/08717/2023) with D129N predominating in Australia, South East Asia, Middle East and Africa; C.5.7 (no reference assigned yet) with E183K and E128G seen in China, Thailand, Europe, Middle East and South Africa. Other C.5 viruses were detected in variable proportions across the globe. No Clade V1A.3 viruses were detected since 1st February 2023. No B/Yamagata lineage viruses have been detected since March 2020. Global geographical distribution of influenza B/Victoria genetic clades (subclades) viruses, obtained with full HA sequences as deposited in GISAID and classified using Nextclade.Geographic markers scaled to detection proportions. Map provided by WHO GIS Centre for Health, DNA/DDI Maximum likelihood phylogenetic tree: B/Victoria Maximum likelihood phylogenetic tree inferred using Iqtree2 from HA sequence data obtained from GISAID from 1st September onwards. Trees were manually curated and, if sequence numbers were > 200, downsampled using Treemer to retain a representative tree topology of 200 sequences with emphasis on viruses from the European region. Annotation of amino acids substitutions was performed with Treetime ancestral reconstruction. References and CVVs are marked as Cell or Egg. 17 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 18 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Summary of the antigenic properties of B/Victoria lineage viruses circulating in the reporting period Very few B/Victoria viruses collected since 1st September have been phenotypically characterized by haemagglutination inhibition (HI). All V1A.3a.2 viruses tested were well‑recognised by antisera raised against B/Austria/1359417/2021 and ‑like viruses. For an overall picture of the past season, see the Annex. B/Victoria: Reagents and references Virus Genetic group Virus passage Ferret ID B/Brisbane/60/2008 V1A E4/E4 sheep pool B/Stockholm/3/2022 V1A.3a.2 SIAT1/MDCK3 F28/22 B/Austria/1359417/2021 V1A.3a.2 SIAT1/MDCK4 NIB F01/21 B/Austria/1359417/2021 G141 V1A.3a.2 E3/E5 F15/21 B/Austria/1359417/2021 G141R V1A.3a.2 E3/E5 F44/21 19 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Antiviral susceptibility testing At the WIC, influenza viruses detected within the WHO EURO Region since 1st September 2023 (weeks 35/2023 to 3/2024) were assessed for phenotypic and/or genotypic susceptibility to antivirals. Of these, 31 A/H1N1, 29 A/H3N2 and 14 B/Victoria viruses were phenotypically assessed against oseltamivir and zanamivir. All viruses showed Normal Inhibition (NI) by both NAIs. Phenotypic testing for susceptibility to baloxavir marboxil was performed for 9 A/H1N1, 8 A/H3N2 viruses and 14 B/Victoria viruses, with all of them showing Normal Inhibition. Genotypic assessment of 79 A/H1N1, 81 A/H3N2 NA AND 10 B/Victoria gene sequences from influenza viruses detected within the WHO EURO Region since 1st September 2023 and received at the WIC did not find any marker associated with reduced susceptibility to NAI. For 55 A/H1N1, 74 A/H3N2 and 8 B/Victoria viruses where PA gene sequencing was successful, no markers associated with reduced inhibition by baloxavir marboxil were identified. Summaries of data submitted to TESSy Genetic characterization (According to the guidance produced for TESSy reporting at the beginning of the 2023‑2024 influenza season) Overall, 1,424 viruses detected fromweek 35/2023 to 3/2024 were genetically characterized: • Of 990 A/H1N1 viruses, all belonged to clade 6B.1A.5a.2 (clade 5a.2) with 490 (49%) represented by A/Sydney/5/2021 (5a.2a), 469 (47%) by A/Victoria/4897/2022 (5a.2a.1) and 24 (2%) by A/Wisconsin/67/2022 (5a.2a.1), while two viruses were unclassified and five (1%) were allocated to the ‘Subgroup Not Listed’ category. • Of 395 A/H3N2 viruses, all belonged to clade (3C.2a1b.2a.2, renamed as 2) with 387 (98%) represented by A/Thailand/8/2022 (clade 2a.3a.1) and five (2%) represented by A/Finland/402/2023 (clade 2a.3a). One H3 virus was unclassified and two (1%) were allocated to the ‘Subgroup Not Listed’ category. • Of 39 B/Victoria‑lineage viruses,all belonged to clade V1A.3a.2, with 27 (69%) represented by B/Catalonia/2279261NS/2023 (subclade C.5.1), seven (18%) represented by B/Connecticut/01/2021 (subclade C.5) and four (10%) represented by B/Austria/1359417/2021 (subclade C). No viruses were allocated to the ‘Subgroup Not Listed’ category. Susceptibility to antivirals Between weeks 35 and 39/2023, 8 viruses were assessed for susceptibility to neuraminidase inhibitors and 7 were assessed for susceptibility to baloxavir marboxil. Phenotypically and/or genotypically, no markers associated with reduced susceptibility were identified. No antiviral susceptibility data was available so far for weeks 40/2023 to 3/2024 of season 2023‑2024. 20 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 Annex Heatmapped phylogenetic trees represent the combined genetic and antigenic analyses where the correlation between genetic groups, signature amino acids and their antigenic profile (including microneutralisation for A/H3N2) can be observed. These outputs were generated by the LondonWHOCollaborating Centre at theWIC for the SH 2024 September VCMwith influenza viruses with collection dates between 1 February and 31 August 2023. A/H1N1 0.003 A/Romania/546347/2023 A/Nordrhein-Westfalen/8/2023 A/Belgium/G0193/2023 A/Victoria/4897/2022 Egg A/Sweden/4722/2023 A/Kosovo/765/2023 A/Champagne Ardenne/05898/2023 A/Belgium/S1333/2023 A/Kosovo/518/2023 A/Bulgaria/1926/2023 A/Belgium/S1330/2023 A/Thuringen/5/2023 A/Sweden/50473/2023 A/Sydney/175/2022 Egg A/Serbia/2348/2023 A/Hong Kong/1514/2023 A/Lisboa/35/2023 A/Slovenia/801/2023 A/Victoria/5172/2022 Cell A/Belgium/S1341/2023 A/Hong Kong/1502/2023 A/Odesa/1936/2023 A/Burgos/4811/2023 A/Kosovo/1221/2023 A/Sweden/4097/2023 A/Albania/290470/2023 A/Argentina/538/2023 A/Estonia/173318/2023 A/Lyon/820/2021 Egg A/Lisboa/49/2023 A/Sweden/5227/2023 A/Ghana/1114/2023 A/Hong Kong/1475/2023 A/Netherlands/10468/2023 Cell A/Guangdong-Maonan/SWL1536/2019 Cell A/Switzerland/77757/2023 A/Ghana/2711/2022 Cell A/Dakar/01/2023 A/Romania/546205/2023 A/Poland/159/2023 A/Antsirabe/01812/2023 A/Belgium/S1359/2023 A/Ile de France/04334/2023 A/Switzerland/40234/2023 A/Norway/3602/2023 A/Argentina/595/2023 A/Sweden/4141/2023 A/Norway/4944/2023 A/Norway/3014/2023 A/Berlin/4/2023 A/Denmark/3280/2019 Cell A/Bosnia and Herzegovina/219/2023 A/Washington/22/2023 Cell A/Switzerland/76467/2023 A/Mauritius/P23333_I-38/2023 A/Poland/109/2023 A/Argentina/736/2023 A/Sweden/5499/2023 A/Norway/31694/2022 Egg A/Slovenia/742/2023 A/Ghana/222/2023 A/Belgium/G0316/2023 A/Mauritius/P10625_I-19/2023 A/Kosovo/929/2023 A/Wisconsin/67/2022 Cell A/Hungary/116/2023 A/Ireland/16836/2023 A/Argentina/605/2023 A/Lisboa/20/2023 A/Fianarantsoa/01808/2023 A/Salalah/5239565/2023 A/Argentina/567/2023 A/Serbia/507608/2023 A/Eskilstuna/3/2023 A/Victoria/2570/2019 Egg A/Netherlands/10259/2023 A/Argentina/535/2023 A/Estonia/173321/2023 A/Ireland/19595/2023 A/Argentina/825/2023 A/Estonia/173456/2023 A/Guangdong-Maonan/SWL1536/2019 Egg A/Bulgaria/1752/2023 A/Maine/10/2022 Cell A/Wisconsin/588/2019 Cell A/Estonia/KL318/2023 A/Bretagne/06091/2023 A/Switzerland/94869/2023 A/Mauritius/P37571/2023 A/Hong Kong/1430/2023 A/Hong Kong/1432/2023 A/Kosovo/948/2023 A/Switzerland/58518/2023 A/Romania/546116/2023 A/Fianarantsoa/01752/2023 A/Argentina/772/2023 A/Argentina/627/2023 A/Kyiv/1996/2023 A/Lisboa/57/2023 A/Romania/547563/2023 A/Slovenia/836/2023 A/Slovenia/714/2023 A/Argentina/533/2023 A/Belgium/S1403/2023 A/Ghana/1160/2023 A/Niedersachsen/9/2023 A/Alsace/09577/2023 A/Hayma/7232071/2023 A/Mauritius/P10754_I-21/2023 A/Lisboa/72/2023 A/Argentina/708/2023 A/FVG-Trieste/115/2023 A/Sydney/5/2021 Egg A/Estonia/173557/2023 A/Antananarivo/01843/2023 A/Belgium/S1785/2023 A/Mauritius/P10318_I-15/2023 A/Ireland/16739/2023 A/Argentina/742/2023 A/Argentina/735/2023 A/Mauritius/P21788_I-27/2023 A/Wisconsin/67/2022 Egg A/Sydney/5/2021 Cell A/Bulgaria/1546/2023 A/Dakar/08/2023 A/Argentina/531/2023 A/Kosovo/1144/2023 A/Ile de France/03351/2023 A/Mauritius/P10431_I-17/2023 A/Brandenburg/2/2023 A/Georgia/12/2022 Cell A/Sichuan-Qingyang/SWL1148/2023 Egg A/Leon/4760/2023 A/Burgos/3972/2023 A/Argentina/563/2023 A/Kosovo/1488/2023 A/Dakar/12/2023 A/Norway/25089/2022 Cell A/Lisboa/56/2023 A/Antsirabe/01811/2023 A/Antsirabe/01814/2023 A/Bayern/7/2023 A/Estonia/173432/2023 A/Netherlands/10245/2023 A/Bulgaria/1762/2023 A/Lisboa/68/2023 A/Hong Kong/1429/2023 A/Belgium/G0310/2023 A/FVG-Trieste/114/2023 A/Argentina/763/2023 A/Netherlands/10294/2023 A/Belgium/S1188/2023 A/Moramanga/01770/2023 A/Argentina/525/2023 A/Norway/5021/2023 A/Kosovo/1305/2023 A/Sachsen/3/2023 A/Saarland/1/2023 A/Valladolid/4861/2023 IVR-215 (A/Victoria/2570/2019) A/Argentina/490/2023 A/Slovenia/438/2023 A/FVG-Trieste/116/2023 A/Kosovo/503/2023 A/Romania/548449/2023 A/Ghana/1894/2021 Egg A/Belgium/G0207/2023 A/Estonia/173338/2023 A/Argentina/630/2023 A/West Virginia/30/2022 Egg A/Slovenia/427/2023 A/Slovenia/656/2023 A/Hong Kong/1512/2023 A/Kosovo/1297/2023 A/Lisboa/75/2023 A/Jaalan Bani Bu Ali/7232311/2023 A/Mauritius/P10187_I-14/2023 A/Washington/24/2023 Cell A/Netherlands/10331/2023 A/Catalonia/NSVH161512065/2022 Egg A/Netherlands/10327/2023 A/Franche Comte/04389/2023 A/Belgium/G0248/2023 A/Brisbane/792/2022 Egg A/Estonia/174171/2023 A/Switzerland/43530/2023 A/Odesa/1935/2023 A/Belgium/S1332/2023 A/Victoria/4897/2022 Cell A/Serbia/2737/2023 A/Argentina/684/2023 IVR-238 (A/Victoria/4897/2022) A/Belgium/S1357/2023 A/Kosovo/497/2023 A/Fianarantsoa/01776/2023 A/Belgium/S1395/2023 A/Moldova/2027110/2023 V427X, N496X I185V M227I E447X E258G K211T V152I S128T, P137S, G155E, T483N, D501N A423X V234I, D274N, K409X A48P T270A V418I S143G H273X S143G, A261V, K488R N455D K43R, A141T, I404V P137S S490T S190X, T270I, V272I V173I, V527I T25A, I510V L191X, A197T, R205K K54Q, A186T, E224A, R259K, K308R E189Q S121N H138Y V187A T216A R205K P137S, T277A, E356D R74K, P183X, A315X S71Y A73E L233I, E243K N130K T82K, N84X G170E, R308G, E491K P271Q A493S P137S I372V R45K A73T, A141E, V152I, S190I Q223R D86N R252X T216I K22R V418I V321A S190X, V418I, T434X D485N, L495X F330X T120K, H273R H399N, D412N S190X D86X, S157L, M257I S190X, I266V D436E A73V, V272I, T483N S137P K211X, V527I T120A, I372V D222N N84X, F330X, N441X, I510V H51Y, S83P, S85P, P137S, H273Q, V321I T270A, V528I K156R I166V, T270K, N496S N370I R113K P137S, D269N G53D, V152I E492X T186A, Q223R I418V K130N, N156K, L161I, A187D, V250A, E506D N84K N31S, M257X I383X E432G R45K K142R, D260E, N451H A392T, K470E S157T Y361F Y468N Q223R R45K S190N V152I L32I, V234X, I460X N84S, R205K, L365Q I533V L526M R205K V527I S326T H352X A48P Q163X A141T, N398S D94E K119R, L314M G394X K402R S190X, R509K Q223R L105X R205K Q223R D35N N370X F111X, D187X, S190X V199X D260G M476I R45K S190X, D260N V379X, T508I V528I A195E T216A I166T, A186T, V187X V152I Q223R D94N K208E R142K S207G A73T A/Bulgaria/234/2023 HI fold changes <4 4 >8 8 N/A Homologous A/Bulgaria/1413/2023 A/Norway/1502/2023 Vaccine viruses Reference viruses Potential CVVs Collection dates Feb 2023 Mar 2023 Apr 2023 May 2023 Jun 2023 Jul 2023 Crick human serology viruses G-M36e 5a.1 G-M36c 5a.1 GHA94e 5a.1 LYO20e 5a.1 DEN80c 5a.2 IVR-215 5a.2 (VIC70e) SYD5c 5a.2a SYD5c 5a.2a NOR89c 5a.2a.1 NOR94e 5a.2a.1 VIC97c 5a.2a.1 IVR-238 5a.2a.1 WIS67c 5a.2a.1 (VIC97e) G-M36e 5a.1 G-M36c 5a.1 GHA94e 5a.1 LYO20e 5a.1 DEN80c 5a.2 IVR-215 5a.2 (VIC70e) SYD5c 5a.2a SYD5c 5a.2a NOR89c 5a.2a.1 NOR94e 5a.2a.1 VIC97c 5a.2a.1 IVR-238 5a.2a.1 WIS67c 5a.2a.1 (VIC97e) 5a.2a.1 5a.2a 5a.2 5a.1 21 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 A/H3N2 0.003 A/Netherlands/10277/2023 A/Belgium/S0898/2023 A/Minnesota/41/2022 Cell A/Ireland/8169/2023 A/Georgia/19/2023 Cell A/South Africa/R06839/2023 A/Slovenia/9318/2022 Egg A/Dijon/04832/2023 A/Switzerland/85635/2023 A/Switzerland/11159/2023 A/Darwin/6/2021 Cell A/Darwin/9/2021 Egg A/Skovde/2/2023 A/South Africa/R06068/2023 A/Estonia/173645/2023 A/Belgium/S1204/2023 A/South Africa/R03796/2023 A/Catalonia/NSVH161512067/2022 Cell A/Hong Kong/1537/2023 A/Norway/3809/2023 A/Switzerland/87207/2023 A/Cameroon/1742/2023 A/Switzerland/95050/2023 A/South Africa/R06131/2023 A/Switzerland/76199/2023 A/Serbia/500898/2023 A/Albania/289813/2022 Egg A/Maryland/02/2021 Egg A/South Africa/R04061/2023 A/Catalonia/NSVH161512067/2022 Egg A/Sichuan-Qingyang/1254/2023 Egg A/Burgos/4012/2023 A/Bulgaria/1427/2023 A/Ireland/9047/2023 A/Estonia/173741/2023 A/Ireland/9045/2023 A/South Australia/389/2022 Egg A/South Africa/R03818/2023 A/Brandenburg/15/2022 Egg A/Singapore/GP12876/2022 Egg A/Baden-Wurttemberg/14/2023 A/Brisbane/837/2022 Cell A/Switzerland/28719/2022 Egg A/Champagne Ardenne/05242/2023 A/South Africa/R05871/2023 A/South Africa/R03513/2023 A/Belgium/G0261/2023 A/Pays de Loire/05590/2023 A/Belgium/S1414/2023 A/Puerto Rico/31/2022 Egg A/Norway/3118/2023 A/Ireland/16381/2023 A/Estonia/173253/2023 A/Cambodia/925256/2020 Cell A/Hong Kong/1539/2023 A/Norway/3821/2023 A/Estonia/173486/2023 A/Norway/5044/2023 A/South Africa/R06064/2023 A/Thailand/8/2022 Egg A/South Africa/R05520/2023 A/Slovenia/9216/2022 Egg A/Massachusetts/18/2022 Cell A/Hong Kong/1540/2023 A/New York/66/2022 Cell A/Norway/29511/2021 Egg A/South Africa/R05834/2023 A/Estonia/173578/2023 A/Switzerland/32862/2023 A/Michigan/41/2022 Cell A/Poland/205/2023 A/Netherlands/10290/2023 A/Valladolid/4167/2023 A/South Africa/R06096/2023 A/Switzerland/20498/2023 A/Michigan/83/2022 Cell A/South Africa/R06126/2023 A/South Africa/R03690/2023 A/Norway/3384/2023 A/Kosovo/891/2023 A/Slovenia/8720/2022 Cell A/Hong Kong/1538/2023 A/Hong Kong/1544/2023 A/Slovenia/657/2023 A/California/45/2023 Cell A/Centre/03353/2023 A/Dijon/04834/2023 A/Norway/2003/2023 A/Hessen/6/2023 A/Belgium/S1372/2023 A/Ireland/9830/2023 A/Bousher/52310940/2023 A/Sweden/4723/2023 A/South Africa/R03715/2023 A/South Africa/R06085/2023 A/Cameroon/2925/2023 A/Berlin/3/2023 A/Victoria/5290/2022 Egg A/Ireland/21983/2023 A/Norway/24873/2021 Cell A/Leon/4319/2023 A/Dijon/04835/2023 A/South Africa/R04953/2023 A/Netherlands/10192/2023 A/Hong Kong/1536/2023 A/Switzerland/71367/2023 A/Ireland/9468/2023 A/Norway/3891/2023 A/Georgia/02/2022 Egg A/Lille/50053/2022 Cell A/Leon/4132/2023 A/Estonia/KL283/2023 A/South Africa/R03608/2023 A/Thuringen/10/2022 Cell A/Cameroon/2919/2023 A/South Africa/R03531/2023 A/Slovenia/526/2023 A/Hong Kong/1543/2023 A/Greece/ILI_249/2023 A/South Africa/R05001/2023 A/Lisboa/69/2023 A/Guizhou-Liuzhite/326/2022 Egg A/South Africa/R06101/2023 A/Belgium/G0171/2023 A/Hong Kong/1535/2023 A/Sydney/732/2022 Egg A/Netherlands/10236/2023 A/Montana/08/2023 Cell A/Darwin/2472/2022 Cell A/South Africa/R03952/2023 A/Florida/57/2022 Cell A/California/123/2022 Cell A/Albania/289813/2022 Cell A/Albania/290243/2022 Egg A/Michigan/60/2022 Egg A/Bosnia and Herzegovina/181/2023 A/Florida/50/2022 Cell A/Albania/290270/2022 Egg A/Valladolid/4550/2023 A/Bosnia and Herzegovina/167/2023 A/Belgium/G0241/2023 A/Belgium/S0888/2023 A/Norway/3170/2023 A/Hong Kong/1542/2023 A/Leon/4311/2023 A/Stockholm/5/2021 Cell A/California/122/2022 Egg A/Canberra/1/2022 Egg A/Burgos/4014/2023 A/Cambodia/e0826360/2020 Egg A/Sweden/3772/2023 A/Norway/24873/2021 Egg A/Sichuan-Gaoxin/1144/2023 Cell A/Burgos/4245/2023 A/Hong Kong/1546/2023 A/Estonia/173616/2023 A/Alaska/01/2021 Egg A/Sweden/3098/2023 A/Ireland/8661/2023 A/Switzerland/64418/2023 A/Poland/97/2022 Cell ---------------------- 2a.2 I140K I25V, V347M, I418V D186N, D225G D225G L431M G78D, D104N D493N L157I, D225G, S262N S145N M536I A196T, L427F D186G P185S, R405K H183F A19S I48T, D190A, N246K R141K V182I D186N, D225G, R269K I25M, S137A H56Y Q57R, L244X F195Y L70I D7N D53N, N96S (+CHO), I192F, N378S D408N I214T D104G, K276R I335V F195Y, I214S, D493E G225D I242M N285I, L409I T10M (-CHO), A93T, A212T, K278R H183F, F525S T135A (-CHO), T167S, N190S S9N L42X, N122I, D225N F79V, I140K Q173L, A212T I140K, R299K K50I, L531V D186A I242M N94D V347M I160K, S186R N165X, D375N I300V P4S, I25V, S145N, R201K, S219Y A163T, K468Q I214T N122I D186N N133D, S209N F195Y S228T D225G D186N V43I Y159N, L164Q, N171K, S186D, D190N, P198S D7G G386E H183F, I242M I140K, I223V G53S A538T N122K S219F S91N E50K I478M F195Y S199P I34V G62E, A476V V223I D225G, Q501H M168I E83K, S265G S91R, I202V G53D T167X (-CHO), K450R R92K, N94S, P227S R92S T135K (-CHO), S145N, N489T N81D, L157F R299K, D408N I160T (+CHO) N122D (-CHO) D7N, D32E, I140M, P227H, N246S T167X (-CHO), P221X, A272V H156S R33Q S262N N190T, S228G D53G E50K V505I T135A (-CHO) D186N V347M N296S, D408N D186N, D513E S91N Vaccine viruses Reference viruses Potential CVVs Collection dates Feb 2023 Mar 2023 Apr 2023 May 2023 Jun 2023 Jul 2023 Crick human serology viruses 1a --------------- 2a.1a 2a.3 ------------- 2a.3b 2a.3a 2a.3a.1 -------- 1a.1 ------------------ 2 2b 2a 2a.1 2a.1b CAM56c 1a CAM60e 1a THU10c 2b STO5c 2a DAR9e 2a NOR73c 2a.3 NOR73e 2a.3 POL97c 2a.2 SLO20c 2a.1 LIL56c 2a.1 CAT76c 2a.1b BRA15e 2a.3a.1 ALB13c 2a.3a.1 ALB13e 2a.3a.1 ALB70e 2a.3a.1 ALB43c 2a.3a.1 THU10c 2b SWI19e 2b STO5c 2a DAR9e 2a SLO20c 2a.1 CAT67c 2a.1b ALB13c 2a.3a.1 ALB13e 2a.3a.1 CAM56c 1a CAM60e 1a THU10c 2b STO5c 2a DAR9e 2a NOR73c 2a.3 NOR73e 2a.3 POL97c 2a.2 SLO20c 2a.1 LIL56c 2a.1 CAT76c 2a.1b BRA15e 2a.3a.1 ALB13c 2a.3a.1 ALB13e 2a.3a.1 ALB70e 2a.3a.1 ALB43c 2a.3a.1 THU10c 2b SWI19e 2b STO5c 2a DAR9e 2a SLO20c 2a.1 CAT67c 2a.1b ALB13c 2a.3a.1 ALB13e 2a.3a.1 HI fold changes <4 4 >8 8 N/A Homologous MN fold changes <2.0 >2.0<=4.0 >4.0<=8.0 >8.0 < (not recognised by antiserum) N/A Homologous D186X V323X D225X 22 WHO EUROPE SURVEILLANCE REPORT Influenza virus characterisation – Summary Europe, January 2024 B/Victoria 0.003 B/Odesa/1930/2023 B/Slovenia/635/2023 B/Mauritius/P23120/2023 B/Parma/10/2023 B/Bulgaria/1860/2023 B/Hungary/64/2023 B/Slovenia/778/2023 B/Moldova/2031294/2023 B/Netherlands/10253/2023 B/Nordrhein-Westfalen/12/2023 B/Mauritius/P24111/2023 B/Hong Kong/6952/2023 B/Haute Normandie/11317/2023 B/Stockholm/6/2023 B/Ireland/9627/2023 B/Bretagne/08463/2023 B/Slovenia/724/2023 B/Alsace/05588/2023 B/Lisboa/56/2023 B/Estonia/173580/2023 B/Antananarivo/01778/2023 B/Brisbane/60/2008 Egg ------------- V1A B/Switzerland/20084/2023 B/Moldova/2030620/2023 B/Odesa/1937/2023 B/Belgium/G0282/2023 B/Belgium/S1273/2023 B/Romania/547838/2023 B/Belgium/S1509/2023 B/Washington/02/2019 Egg B/Hessen/9/2023 B/Tajikistan/1563/2023 B/Bosnia and Herzegovina/261/2023 B/Ireland/23609/2023 B/Mauritius/P23817/2023 B/Netherlands/10264/2023 B/Estonia/173928/2023 B/Netherlands/11267/2022 Cell B/Slovenia/726/2023 B/Moldova/2027197/2023 B/Bulgaria/1896/2023 B/Switzerland/51774/2023 B/Skovde/1/2023 B/Bulgaria/1915/2023 B/Mauritius/P37214/2023 B/Burgos/4840/2023 B/Hong Kong/15/2023 B/Stockholm/3/2022 Cell B/Estonia/KL484/2023 B/Lisboa/50/2023 B/Ireland/21113/2023 B/Romania/549662/2023 B/Belgium/S1420/2023 B/Bulgaria/1823/2023 B/Salamanca/4831/2023 B/Estonia/173900/2023 B/Bulgaria/1830/2023 B/Ireland/23071/2023 B/Sweden/5553/2023 B/Slovenia/1052/2023 B/Belgium/G0178/2023 B/Norway/5200/2023 B/Serbia/1428/2023 B/Parma/11/2023 B/Leon/4901/2023 B/Salamanca/4828/2023 B/Antsirabe/01813/2023 B/Bulgaria/1808/2023 B/Bretagne/08376/2023 B/Norway/3989/2023 B/Romania/546872/2023 B/Salamanca/4851/2023 B/Norway/5216/2023 B/Tajikistan/1728/2023 B/Slovenia/732/2023 B/Ireland/17764/2023 B/Moldova/2031620/2023 B/Serbia/2225/2023 B/Basse Normandie/05466/2023 B/Switzerland/43256/2023 B/Bulgaria/1643/2023 B/Ireland/15857/2023 B/Shaanxi-Baota/1278/2022 Egg B/Slovenia/979/2023 B/Netherlands/10191/2023 B/Ireland/18976/2023 B/Switzerland/97262/2023 B/Ireland/18570/2023 B/Antananarivo/01799/2023 B/Switzerland/24464/2023 B/FVG-Gorizia/34/2023 B/Burgos/4810/2023 B/Netherlands/10894/2022 Egg B/Burgos/4893/2023 B/Bulgaria/1646/2023 B/Lisboa/47/2023 B/Connecticut/01/2021 Egg B/Slovenia/743/2023 B/Parma/16/2023 B/Estonia/173429/2023 B/Slovenia/924/2023 B/Sweden/5308/2023 B/Sweden/5500/2023 B/Ireland/14244/2023 B/Estonia/174174/2023 B/Moramanga/01789/2023 B/Serbia/1124/2023 B/Estonia/173585/2023 B/Armenia/600/2023 B/Netherlands/10335/2023 Cell B/Estonia/173317/2023 B/Perugia/4/2023 B/Romania/548499/2023 B/Moldova/2030521/2023 B/Bayern/6/2023 B/Segovia/4864/2023 B/Hong Kong/8442/2023 B/Lisboa/45/2023 B/Slovenia/500/2023 B/Bremen/4/2023 B/Catalonia/2279261NS/2023 Egg B/Sweden/5454/2023 B/Norway/3749/2023 B/Fianarantsoa/01942/2023 B/Moldova/2030885/2023 B/Belgium/G0182/2023 B/Serbia/1415/2023 B/Moldova/2030891/2023 B/Paris/06391/2023 B/Belgium/G0192/2023 B/Kyiv/1985/2023 B/Austria/1359417/2021 Egg G141 B/Switzerland/6471/2023 B/Moldova/2030527/2023 B/Catalonia/2279261NS/2023 Cell B/Zhejiang-Xiacheng/11085/2021 Egg B/Norway/3607/2023 B/Champagne Ardenne/04851/2023 B/Netherlands/10486/2023 B/Karlstad/1/2023 B/Switzerland/528/2023 B/Ireland/11305/2023 B/Switzerland/213/2023 B/Slovenia/11466/2022 Cell B/Austria/1359417/2021 Cell B/Belgium/S1782/2023 B/Serbia/2781/2023 B/Boras/1/2023 B/Slovenia/853/2023 B/Parma/15/2023 B/Pays de Loire/08365/2023 B/Switzerland/64703/2023 B/Bulgaria/1929/2023 B/Tajikistan/1314/2023 B/Netherlands/10316/2023 B/Mauritius/P23195_I-37/2023 B/Nordrhein-Westfalen/13/2023 B/Colorado/05/2022 Cell B/Hungary/40/2023 B/Belgium/S1322/2023 B/Mauritius/P23811/2023 B/Kyiv/2021/2023 B/Poland/157/2023 B/Norway/5172/2023 B/Norway/3226/2023 B/Sweden/4139/2023 B/Bretagne/08762/2023 B/Switzerland/55100/2023 B/Zhejiang-Nanhu/1854/2021 Egg B/Catalonia/3514402NS/2023 Egg B/Orebro/1/2023 B/Belgium/S1957/2023 B/Estonia/174175/2023 B/Hungary/126/2023 B/Tsiroanomandidy/01848/2023 B/Colorado/06/2017 Egg ------------- V1A.1 B/Belgium/G0187/2023 B/Lisboa/58/2023 B/Lisboa/57/2023 B/Switzerland/53639/2023 B/Salamanca/4829/2023 B/Bulgaria/1734/2023 B/FVG-Gorizia/33/2023 B/Ireland/13684/2023 B/Belgium/S1933/2023 B/Armenia/622/2023 B/Bosnia and Herzegovina/256/2023 B/Berlin/18/2023 B/Estonia/173587/2023 B/Austria/1359417/2021 Egg G141R B/Bulgaria/1485/2023 B/Romania/550752/2023 B/Palencia/4842/2023 B/Slovenia/758/2023 B/Bulgaria/1756/2023 B/Salamanca/4852/2023 B/Nordrhein-Westfalen/9/2023 B/Norway/5159/2023 B/Mauritius/P10571_I-20/2023 V117I, E128K, A154T, K326R V252M I117N, N129D, E183K, S510F T199A (-CHO) G133R, N197S (-CHO) G256R, V379I T170I, D197N (+CHO), V559I I246V E48K N43S T199A (-CHO), I551V T121A, S476X R118K G141R K136E, del(162-164) A154E, V252M V29A A169T, D196X T189A H122Q G528R T199A (-CHO) E183K E183K G141R K75E, E128K, T155A, G184R, G230N T438A S255P T262S A169T, K279N I553V T221A E128G R118K I267V T221I E198G S539A A66S N126S D129N, G256E I175M V190I A169V T73I, I137V V177I V379I T548A I3V E128G, E183K E183K V556I, V559I E128K, A154E, S208P A276X, V379I T127I, E183K H532Y, I568L I318V, A464X T199A (-CHO) D526E D129G R498K D197E E198K N145D E184K N123K K71X, K281R T222A E429G R80G, E184K E198G, V559I V555I E198G D207N, L496X P172L Y179X, T258A D497N V379I V87I, T121N V87A Q200P E183K T37I, E197X T182A, D197E D129G, del(162-163), I180V, N197X (-CHO), R498K E128K A127T, P144L, N150K, G184E, N197D (-CHO), K203R, R279K G141R I499X T258X G415X I267X G351X V117X P328X G278X T372X E136X G230X B/Netherlands/10335/2023 Egg D515X Vaccine viruses Reference viruses Potential CVVs Collection dates Feb 2023 Mar 2023 Apr 2023 May 2023 Jun 2023 Jul 2023 Crick human serology viruses V1A.3 V1A.3a.2 BRI60e V1A COL06e V1A.1 WAS02e V1A.3 NET67c V1A.3 NET94e V1A.3 AUS17c V1A.3a.2 AUS17eG V1A.3a.2 AUS17eR V1A.3a.2 STO3c V1A.3a.2 NET35e V1A.3a.2 CAT02e V1A.3a.2 CAT61e V1A.3a.2 BRI60e V1A COL06e V1A.1 WAS02e V1A.3 NET67c V1A.3 NET94e V1A.3 AUS17c V1A.3a.2 AUS17eG V1A.3a.2 AUS17eR V1A.3a.2 STO3c V1A.3a.2 NET35e V1A.3a.2 CAT02e V1A.3a.2 CAT61e V1A.3a.2 HI fold changes <4 4 >8 8 N/A Homologous WHO Collaborating Centre reports A full description of results generated by the London WHO Collaborating Centre at the WIC and used at the September 2023 WHO VCM, and previous ones, can be found at https://www.crick.ac.uk/partnerships/world wide‑influenza‑centre/annual‑and‑interim‑reports 23 European Centre for Disease Prevention and Control (ECDC) Gustav den III:s Boulevard 40, SE-169 73, Solna, Sweden Tel. +46 858 60 10 00 Fax +46 858 60 10 01 www.ecdc.europa.eu Contact us publications@ecdc.europa.eu Follow us on Twitter @ECDC_EU Like our Facebook page www.facebook.com/ECDC.EU World Health Organization Regional Office for Europe UN City, Marmorvej 51, DK-2100 Copenhagen Ø, Denmark Tel. +45 45 33 70 00 Fax +45 45 33 70 01 www.who.int/europe Contact us eurocontact@who.int Follow us on Twitter @WHO_EUROPE Like our Facebook page www.facebook.com/WHOEurope WHO/EURO:2024-6189-45954-73244