Weekly influenza surveillance overview, February 25, 2011 - Week 7

Most European countries reported medium influenza-like illness /acute respiratory infection consultation rates and widespread activity. Decreasing ILI/ARI trends were reported by 17 countries.The proportion of influenza virus-positive sentinel specimens has gradually decreased to 40% after peaking in week 52/2010 at 57%.In week 7/2011, Sixty-seven per cent of influenza virus detections in week 7/2011 were type A, 33% were type B. More than 98% of subtyped influenza A viruses were A(H1N1)2009. Six countries reported B virus as dominant and seven countries as co-dominant.In week 7/2011, ten countries reported 151 all-cause SARI and hospitalised confirmed influenza cases, the latter mostly due to influenza virus A(H1N1)2009 infection.Numbers of influenza infections with severe outcome have decreased in western European Union countries (Denmark, France, the Netherlands, Ireland, Spain and the UK). However, numbers have risen considerably in Greece in recent weeks and there is considerable uncertainty about severe cases in a number of other countries in central and eastern European countries because of limited hospital surveillance for influenza-associated cases.