Pandemic (H1N1) 2009 - update 80
Weekly virological surveillance update
23 December 2009 - For this reporting week (6 to 12 December 2009); a total of 28 countries reported to FluNet. The total number of specimens reported positive for influenza viruses was 9507. Of these, 8628 (90.8%) were pandemic A(H1N1) 2009, 94 (1.0%) were seasonal A (H1), 105 (1.1%) were A (H3), 528 (5.6%) were A (not subtyped), and 152 (1.6%) 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 19th December, cumulatively 153 countries/areas/territories shared a total of 20520 specimens (15648 clinical samples and 4872 virus isolates) with WHO CCs. Of these, 15356 specimens (clinical samples and isolates) were tested; 12312 (80.2%) were positive for influenza viruses. Of these positives, 8179(66.4 %) were pandemic A(H1N1), 3314(26.9%) were seasonal influenza A, and 804 (6.5%) were influenza B.
Systematic surveillance conducted by the Global Influenza Surveillance Network (GISN) including WHOCCs, continues to detect sporadically pandemic A (H1N1) viruses that are resistant to oseltamivir. So far, antiviral susceptibility testing was conducted by WHO CCs and other GISN labs on pandemic A (H1N1) specimens and isolates from at least 86 countries, and 168 cases of oseltamivir resistance have been reported by GISN so far.
All of these viruses showed H275Y mutation but all these viruses remain sensitive to zanamivir. Worldwide, more than 15,000 clinical specimens (samples and isolates) of the pandemic A (H1N1) virus have been tested and found to be sensitive to oseltamivir.
All pandemic A(H1N1) 2009 influenza viruses analysed to date were antigenically and genetically closely related to the vaccine virus A/California/7/2009.
WHO, through the Global Influenza Surveillance Network (GISN), continues monitoring the evolution and global circulation of influenza viruses, including pandemic, seasonal and other influenza viruses infecting, or with the potential to infect humans.