Since 01 January 2012, influenza A(H1N1)pdm09, influenza A(H3N2), and influenza B/Victoria- and B/Yamagata-lineage viruses have been detected in ECDC-affiliated countries.

• Type A viruses have predominated over type B.
• A(H3N2) viruses have predominated over A(H1N1)pdm09 viruses.
• A(H1N1)pdm09 viruses continue to show genetic drift from the vaccine virus, A/California/07/2009, but the vast majority are antigenically similar to A/California/07/2009.
• During this time period, all A(H3N2) viruses sequenced fell within five genetic groups. Test viruses isolated in mammalian cells show low titres with post-infection ferret antisera raised against egg-propagated viruses, including the new vaccine virus A/Victoria/361/2011. They react well with post-infection ferret antisera raised against A/Victoria/361/2011 and other current reference viruses exclusively propagated in tissue culture.
• Recent B/Victoria lineage viruses fell within the B/Brisbane/60/2008 genetic clade and were antigenically similar to reference cell-propagated viruses of the B/Brisbane/60/2008 genetic clade.
• Recent B/Yamagata-lineage viruses fell into two genetic clades, the B/Bangladesh/3333/2007 and B/Wisconsin/1/2010 genetic clade or into the B/Brisbane/3/2007 genetic clade; viruses in these clades are antigenically distinguishable.