WORLD HEALTH ORGANIZATION
ORGANISATION MONDIALE DE LA SANTE
REGIONAL OFFICE FOR THE WESTERN PACIFIC BUREAU REGIONAL DU PACIFIQUE OCCIDENTAL
REGIONAL COMMITTEE Sixtieth session Hong Kong (China) 21–25 September 2009 Provisional agenda item 15
WPR/RC60/INF.DOC.2 9 September 2009 ORIGINAL: ENGLISH
UPDATE ON PANDEMIC (H1N1) 2009
Just seven weeks after the Pandemic (H1N1) 2009 virus emerged in Mexico in April 2009, it had spread across all areas of the Western Pacific Region, moving much faster than previous pandemics. The current epidemiological situation varies among the 37 countries and areas that make up the Western Pacific Region, with countries in the northern hemisphere not yet in flu season expecting an increase in the number of cases while countries in the southern hemisphere have past their winter flu season peak. The majority of Pandemic (H1N1) 2009 patients experience mild flu-like symptoms and recover fully, only requiring ambulatory care. The majority of severe and fatal cases have been young adults with underlying medical conditions. Pregnant women, particularly those in their second and third trimesters, appear to be more likely to experience severe illness — and death — if infected with the virus. The variation in the reported data about suspected and confirmed cases makes it difficult to estimate a case fatality rate, with estimates ranging from 0.1% to 0.5%. The predominant strain of influenza virus circulating in the Region is Pandemic (H1N1) 2009. The strain is not similar to the H5N1 or 1918 pandemic influenza virus. The virus has remained stable and there are no signs of reassortment with the H1 or H3 seasonal influenza viruses. The Pandemic (H1N1) 2009 virus is sensitive to the neuraminidase inhibitors Oseltamivir and Zanamivir, but resistant to adamantine (Amantadine). There have been a few reported cases of Oseltamivir resistance, but all have recovered and no further transmission has been observed. Several vaccine trials are ongoing and a vaccine is expected to be available by midOctober 2009. Supply is likely to be limited, with global production capacity estimated to be limited to 4.9 billion doses annually. The impact of the Pandemic (H1N1) 2009 virus has not yet been fully realized. Countries should prepare for a significant surge in health care (including intensive care) demand and extensive community-level transmission. Countries need to prepare for a change in disease severity and the development of drug resistance to available medications, as well as for adverse reactions to the vaccine.
WPR/RC60/INF.DOC.2 page 2
SITUATION ANALYSIS Epidemiology The first cases of Pandemic (H1N1) 2009 were identified in the Region in New Zealand on 28 April, among a group that went to Mexico for a school trip. Within seven weeks the virus had spread to the entire Western Pacific Region. The age distribution of those ill with Pandemic (H1N1) 2009 is different from that of seasonal influenza, being skewed towards younger age groups. Infections among people over 65 years are notably low, making up only 5% of all reported infections. There were no noticeable differences observed between the sexes. The route of transmission and incubation period of the Pandemic (H1N1) 2009 virus is similar to that of seasonal influenza, however the pandemic strain seems to be infective (i.e., sheds the virus) for a longer period than usual seasonal influenza. The United States Centers for Disease Control and Prevention reports that Pandemic (H1N1) 2009 transmissibility is lower than seasonal influenza, however this statement still needs to be confirmed by observations in the field. At present, only a handful of cases of virus resistance to Oseltamivir have been detected despite the administration of many millions of courses of antiviral drugs worldwide. No onward transmission of drug-resistant virus has been documented. Intense monitoring continues through the WHO’s network of laboratories. The genetic structure of the Pandemic (H1N1) 2009 virus has been described and continues to be monitored closely. To date, the virus remains stable and there is no evidence of mutation or significant "drift" having occurred. Countries in the northern hemisphere continue to report increased numbers of cases and deaths associated with Pandemic (H1N1) 2009. They also report that the Pandemic (H1N1) 2009 strain of the virus is by far the most prevalent influenza strain circulating at the moment. The northern hemisphere generally moves into its winter flu season in November or December, however Japan has moved into flu season in September of this year, much earlier than is usual. Since late August there has been an overall downward trend in influenza activity in countries located in the southern hemisphere. In tropical areas, influenza-like activity trends vary from country to country.
WPR/RC60/INF.DOC.2 page 3 Risk assessment The estimated proportion of people infected with Pandemic (H1N1) 2009 in the Western Pacific Region ranges from 10% to 25%. While the vast majority of people infected with Pandemic (H1N1) 2009 experience mild flu-like symptoms and recover in the ambulatory care setting, between 2% and 9% of cases require hospitalization, of which 15% to 35% were reported to have severe illness. The fatality rate for Pandemic (H1N1) 2009 is difficult to ascertain, but best estimates indicate that associated mortality is between 0.1% and 0.5%. Some 75% to 85% of fatal cases had an underlying medical condition. Because the pandemic involves a novel strain of influenza, it is expected that more people will be affected by influenza this year than in previous years. The surge in people seeking health care for influenza-like illness has the potential to overwhelm primary and secondary health care services, including front-line clinics, public health services, hospital emergency departments, laboratories and intensive care units. Further, higher rates of absenteeism — as staff become ill themselves or are providing care for their own dependants — and increased mandatory surveillance and reporting requirements may contribute to overwhelming key public health infrastructure and systems. Strong infection-control practice will be vital in preventing spread of the virus in health care facilities. The relatively high proportion of people that require ventilation and intensive care will put additional strain on critical care services and will need to be managed to minimize opportunity costs. Many patients admitted to an intensive care unit required between 10 and 20 days of care. Evidence from Australia, Canada and New Zealand indicate that indigenous people are at two to four times greater risk of severe illness than the general populations in those countries. This increased risk is attributable to higher levels of co-morbidities, barriers to early access to health care, poor living conditions, and other negative social determinants of health. People with underlying medical conditions including respiratory, cardiac, renal and metabolic disorders are at higher risk of severe illness and death. Some 75% to 85% of fatal cases had an underlying medical condition. Also, pregnant women, particularly if in their second and third trimester, are at increased risk of complications and death. The very young — children less than 2 years old — and the very old are more likely to experience severe illness because of weakened immune systems and sensitivities to treatment procedures and requirements. In some cases, delayed access to antiviral medication may have been a contributing factor to death.
WPR/RC60/INF.DOC.2 page 4 Response Ongoing risk assessment The speed of the response is essential. National and local authorities need to swiftly assess the local epidemiological situation, local risk factors, demographic context and resource availability in order to determine the most effective response to this threat. National authorities must base their response strategies on their own risk assessments. Local knowledge is critical in determining appropriate public health responses to suit desired public health objectives at different stages of the pandemic. Surveillance Improved national surveillance systems, laboratory capacities and pandemic preparedness in recent years have greatly helped in responding to the current pandemic. As the spread of Pandemic (H1N1) 2009 is inevitable, response strategies will need to change. At different phases, governments will need to adapt public health surveillance and response strategies, as well as laboratory testing strategies, based on the evolving pandemic situation in their country and region to better utilize the limited resources to mitigate the pandemic’s impact. Pharmaceutical interventions Early recognition of symptoms and the provision of timely medical care, including the administration of antiretroviral drugs, are keys to limiting the spread of the virus and saving lives, particularly in high-risk groups. Globally, 25 companies have indicated their intention to produce a Pandemic (H1N1) 2009 vaccine, with vaccines expected to be available later this year. As initial vaccine supplies will not be sufficient to cover entire populations, national authorities will need to consider their approach to the roll-out of vaccination programmes. In order to protect essential health infrastructure and prevent spread of the virus in health care settings, WHO recommends health care workers be given high priority for vaccination. Further, WHO recommends that governments take a staged approach to prioritize vaccination of high-risk groups, based on available epidemiological evidence. Risk communication Public communication is a vital component of the response to Pandemic (H1N1) 2009. While it is acknowledged that it is difficult to communicate risks when there is much uncertainty, good risk
WPR/RC60/INF.DOC.2 page 5 communication messaging and behaviour change communication are key to an effective public health response. IHR communication While the pandemic continues to evolve, communication under the International Health Regulations (2005) mechanisms remains a critical link for disease reporting and regional and global monitoring to detect shifts in severity, mortality, drug resistance and virus changes. The International Health Regulations (2005) mechanism supports the global response to the pandemic.