Global Alert and Response (GAR)

Pandemic (H1N1) 2009 - update 70

Weekly update (Virological surveillance data)

The Global Influenza Surveillance Network (GISN) continues monitoring the global circulation of influenza viruses in particular those infecting or with the potential of infecting humans including seasonal influenza.

Since the beginning of the pandemic in 19 April 2009 to 3 October 2009, a total of 80 countries reported to FluNet. The total number of specimens reportedly positive for influenza viruses by NIC laboratories was 142,777. Of these, 87,776 (61.5%) were pandemic H1N1, 6773 (4.7%) were seasonal A (H1), 19,499 (13.7%) were A (H3), 24,331 (17%) were A (Not subtyped) and 4398 (3.1%) were influenza B.

For this reporting week (27 September to 3 October 2009); a total of 28 countries reported to FluNet. The total number of specimens reportedly positive for influenza viruses by NIC laboratories was 6378. Of these, 4012 (62.9%) were pandemic H1N1, 59 (0.9%) were seasonal A (H1), 394 (6.2%) were A (H3), 1785 (28%) were A (Not subtyped), 128 (2%) were influenza B.

Systematic surveillance conducted by the Global Influenza Surveillance Network (GISN) including WHO Collaborating Centres (WHOCCs) for reference and research on influenza, continues to detect sporadic incidents of H1N1 pandemic viruses that show resistance to the antiviral oseltamivir. To date, 35 resistant pandemic H1N1 influenza viruses have been detected and characterized worldwide. All of these viruses show the same H275Y mutation that confers resistance to the antiviral oseltamivir, but not to the antiviral zanamivir. Worldwide, more than 10,000 clinical specimens (samples and isolates) of the pandemic H1N1 virus have been tested and found to be sensitive to oseltamivir.

All pandemic H1N1 2009 influenza viruses analysed to date were antigenically and genetically closely related to the vaccine virus A/California/7/2009.

Virology data update

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