Weekly influenza surveillance overview, 24 February 2012 - week 7

The national influenza season epidemics in Europe may be approaching their peak in the first affected countries and remain dominated by A(H3) viruses. The influenza A(H3) and B viruses circulating this season have moved genetically and antigenically away from 2011–2012 seasonal vaccine viruses which has prompted WHO to recommend different vaccine viruses for the 2012-2013 seasonal vaccine. This is reported in the latest edition of the ECDC Weekly Influenza Surveillance Overview.

During week 7/2012 medium intensity was reported by 16 countries while two countries reported high intensity. Geographic spread was reported as widespread by 11 countries, regional by six, local by four and sporadic by six.

Typical for the 2011-2012 influenza season is that it started later than in recent seasons and has been without any clear geographic progression.

Virological surveillance for the period shows that out of 1 873 sentinel specimens tested, 927 (49.5%) were positive for influenza virus. Of the 2 901 influenza viruses detected from sentinel and non-sentinel sources during week 7, 2 788 (96.1%) were type A and 113 (3.9%) were type B. Of the 1 085 influenza A viruses sub-typed, 1 065 (98.2%) were A(H3) and 20 (1.8%) were A(H1)pdm09.

No resistance to the neuraminidase inhibitors (oseltamivir and zanamivir) has been reported so far this season.