Pandemic (H1N1) 2009 - update 85
Weekly virological surveillance update
29 January 2010 - Pandemic influenza A(H1N1) 2009 virus activity continued to decline in many countries in the Northern Hemisphere. The pandemic A(H1N1) continues to be the predominant circulating influenza virus in nearly all countries where influenza is reported. The most recent available data showed that pandemic A(H1N1) 2009 accounted for 100% of influenza A virus subtype detections in sentinel specimens in WHO EUR (1) and more than 98% in WHO AMR (2) . China on the other hand reported outbreaks due to influenza B (48.8% of all influenza positive specimens). Sporadic detections of seasonal A(H1N1), A(H3N2) and influenza B viruses were reported from a few countries such as Iran, Japan, the Russian Federation and Tunisia.
A total of 25 countries reported to FluNet during the period 10th January 2010 to 16th January 2010. Based on FluNet reporting, the total number of specimens reportedly positive for influenza viruses by NIC laboratories was 3,044. Of these, 1,961 (64.4%) were typed as influenza A and 1,083 (35.6%) as influenza B. Of all sub-typed influenza A viruses, 95% (1,637/1,724) were pandemic (H1N1) 2009.
Since the beginning of the pandemic in 19 April 2009 to 23th January,2010, cumulatively 153 countries shared a total of 23743 specimens (18368 clinical samples and 5375 virus isolates) with WHO CCs for further analysis. All pandemic A(H1N1) 2009 influenza viruses analysed to date appear to be antigenically and genetically closely related to the vaccine virus A/California/7/2009. The pandemic A(H1N1) 2009 viruses with D222G substitution have also been seen antigenically indistinguishable to the A/California/7/2009 (H1N1) vaccine virus.
The WHO Global Influenza Surveillance Network (GISN) including WHOCCs conducts systematic surveillance for antiviral susceptibility. So far, antiviral susceptibility testing conducted by WHO CCs and other GISN laboratories on pandemic A (H1N1) specimens and isolates from at least 88 countries indicates that oseltamivir resistant pandemic H1N1 viruses are sporadic detections with rare onward transmission. So far, 220 cases of oseltamivir resistance have been reported by GISN and other partners. All of these viruses showed the H275Y substitution and all remain sensitive to zanamivir.
WHO, through the 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.
*Some NICs report data to FluNet retrospectively and updates of previous data with new results are frequent.