Pandemic (H1N1) 2009 - update 78
Weekly update (more data on virological surveillance)
11 December 2009 - The Global Influenza Surveillance Network (GISN) continues monitoring the global circulation of influenza viruses, including pandemic, seasonal and other influenza viruses infecting, or with the potential to infect, humans including seasonal influenza.
Since the beginning of the pandemic in 19 April 2009 to 28 November, a total of 82 countries reported to FluNet. The total number of specimens reportedly positive for influenza viruses by NIC laboratories was 337,902. Of these, 246,571 (73%) were pandemic H1N1, 8245 (2.4%) were seasonal A (H1), 23,675 (7%) were A (H3), 53,479 (15.8%) were A (not subtyped) and 5932 (1.8%) were influenza B.
For this reporting week (22 November to 28 November 2009); a total of 24 countries reported to FluNet. The total number of specimens reportedly positive for influenza viruses by NIC laboratories was 14,267. Of these, 12,758 (89.4%) were pandemic H1N1, 118 (0.8%) were seasonal A (H1), 137 (1%) were A (H3), 1182 (8.3%) were A (not subtyped), 72 (0.5%) were influenza B.
The above numbers represent only the specimens and results reported to FluNet. Some laboratories (NICs), under pressure of the pandemic surge, do not test for seasonal subtypes and accordingly, this data should be interpreted with caution.
Detailed virological information for the European Region of WHO is included in the EuroFlu Weekly Electronic Bulletin.
Since the beginning of the pandemic in 19 April 2009 to 5 December, cumulatively 150 countries shared a total of 19523 specimens (15037 clinical samples and 4486 virus isolates) with WHO CCs. Of these, 14097 specimens (clinical samples and isolates) were tested; 11307 (80.2%) were positive for influenza viruses. Of these positives, 7444 (65.8 %) were pandemic H1N1, 3052 (27%) were seasonal influenza A, 796 (7.1%) were influenza B.
A virus mutation at position 222 of the amino acid sequence of the haemagglutinin protein of the pandemic virus was recently reported in a few viruses from Norway. The mutation is D222G (aspartic acid to glycine), which, according to a public accessible gene sequence database "GenBank", has also been detected sporadically in viruses from several other countries like Brazil, China, Japan, Mexico, Italy, Finland, France, Ukraine, US and Hong Kong. since April 2009. This change in the virus has been found in mild as well as severe cases. WHO, through its Global Influenza Surveillance Network (GISN) is monitoring virus mutations that are of potential public health importance.
Systematic surveillance conducted by the GISN including WHOCCs for reference and research on influenza, continues to detect sporadic incidents of H1N1 pandemic viruses that show resistance to the antiviral oseltamivir. Antiviral susceptibility testing was carried out by WHO CCs and GISN labs on specimens and isolates of pandemic H1N1 viruses from at least 31 countries. 102 cases of oseltamivir resistant pandemic H1N1 have been reported from GISN so far.
All of these viruses show the same H275Y mutation. All these viruses remain sensitive to 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.