Biosecurity

Influenza virus characterisation, Summary Europe, February 2016

From week 40/2015, the start of weekly reporting on influenza activity in the WHO European Region, to week 07/2016 over 70 000 influenza detections across the Region have been reported. Influenza type A viruses are prevailing over type B but, unlike the situation in the 2014–15 season, A(H1N1)pdm09 viruses are prevailing over A(H3N2), and the proportion of B/Victoria-lineage detections has risen substantially, representing ~92% of those ascribed to a B virus lineage.   To date, 23 EU/EEA countries have shared 424 influenza-positive specimens with the Francis Crick Institute, London, for detailed characterisation: 16 additional countries and 330 specimens since the December 2015 report. Since the latter report, 230 viruses have been characterised antigenically and genetic analyses are ongoing.   The 166 A(H1N1)pdm09 viruses characterised antigenically were similar to the vaccine virus A/California/7/2009. Worldwide new genetic sub-clusters of viruses within the 6B clade have emerged, with two being designated as subclades: 6B.1 defined by HA1 amino acid substitutions S162N and I216T and 6B.2 defined by HA1 amino acid substitutions V152T and V173I. Of the 123 viruses characterised genetically, 18 (14%) were clade 6B, 98 (80%) were subclade 6B.1 and seven (6%) were subclade 6B.2.