Epidemiological and virological situation update of the 2010/2011 influenza season in the WHO European Region (Week 40/2010 to Week 03/2011)

This overview of influenza data from the WHO European Region from weeks 40/2010 through week 3/2011 has been submitted for consideration during the WHO Northern Hemisphere Vaccine Strain Selection Meeting, to be held on 14-17 February, 2011, in Geneva. The 2010/2011 influenza season arrived 8-10 weeks later than the 2009/2010 ‘pandemic’ season in the WHO European Region, but still quite early compared to historical trends. As has been observed in several previous years, the 2010/2011 influenza season appears to be progressing in a West to East fashion across much of Europe. Increases in influenza activity have been accompanied by increases in hospitalised Severe Acute Respiratory infections (SARI) and in severe influenza cases admitted to intensive care units. Pandemic influenza A (H1N1) 2009 viruses are the predominant circulating viruses but in contrast to the 2009/2010 season, there is a higher rate of co-circulation with influenza B viruses and a substantial decrease in the proportion of influenza A(H3N2) viruses. Currently, 98% of antigenically characterized viruses from the 2010/2011 influenza season correspond with the viruses recommended by WHO for inclusion in the 2010-2011 northern hemisphere influenza vaccine.