Pandemic (H1N1) 2009 - update 77
Weekly update (more data on virological surveillance)
4 December 2009 - Since the beginning of the pandemic in 19 April 2009 to 21 November, a total of 82 countries reported to FluNet. The total number of specimens reportedly positive for influenza viruses by NIC laboratories was 309,204. Of these, 220,641 (71.4%) were pandemic H1N1, 8130 (2.6%) were seasonal A (H1), 23,531 (7.6%) were A (H3), 51,071 (16.5%) were A (Not subtyped) and 5831 (1.9%) were influenza B.
For this reporting week (15 November to 21 November 2009); a total of 22 countries reported to FluNet. The total number of specimens reportedly positive for influenza viruses by NIC laboratories was 10,364. Of these, 9643 (93%) were pandemic H1N1, 104 (1%) were seasonal A (H1), 88 (0.8%) were A (H3), 467 (4.5%) were A (Not subtyped), 62 (0.6%) 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.
From the start of H1N1 pandemic (19 April) till 28th November 2009, cumulatively 150 countries shared a total of 19284 specimens (14879 clinical samples and 4405 virus isolates) with WHO CCs for confirmatory diagnosis and further characterization.
A mutation of D222G in the amino acid sequence of the haemagglutinin protein of the pandemic virus is being monitored by GISN. In addition to Norway, the mutation has also been observed in Brazil, China, Chinese Taipei, Finland, France, Italy, Japan, Mexico, Spain, , Ukraine, and USA, in both severe and mild cases.
Systematic surveillance conducted by GISN laboratories continues to detect incidents of H1N1 pandemic viruses that show resistance to the antiviral oseltamivir. Antiviral susceptibility testing has been carried out on pandemic H1N1 specimens and isolates from at least 31 countries. 96 cases of oseltamivir resistant pandemic H1N1 have been reported from GISN so far. All of these viruses show the same H275Y mutation, but remain sensitive to zanamivir.