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16 Jan 2013
Influenza virus characterisation summary Europe December 2012

The latest issue of ECDC’s monthly series on 'Influenza virus characterisation’ covers the time period from September to December 2012. It is a follow-up of the previous month's report.

Since 1 September 2012, A(H1N1)pdm09, A(H3N2) and B/Victoria and B/Yamagata lineage influenza viruses have been detected in relatively low numbers in ECDC-affiliated countries. The report summarises the findings as follows:

Type A and type B viruses are co-circulating in approximately equal proportions.

A(H3N2) and A(H1N1)pdm09 viruses have been detected at comparable levels, with a recent rise in the proportion of A(H1N1)pdm09 viruses.

A(H1N1)pdm09 viruses continued to show genetic drift from the vaccine virus, A/California/07/2009, but the vast majority remained antigenically similar to it.

The vast majority of A(H3N2) viruses have been antigenically similar to A/Victoria/361/2011, the vaccine virus for the 2012–13 influenza season.

B/Victoria lineage viruses fell within, 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: clade 2 represented by B/Estonia/55669/2012, and clade 3 represented by B/Wisconsin/1/2010 (the vaccine component for the 2012–13 influenza season). Clade 2 viruses have predominated over clade 3.

The next influenza virus characterisation report will be published in March 2013 and will cover data on the 2012-2013 influenza season from September 2012 to February 2013.

For further details, download the complete report 'Influenza virus characterisation - Summary Europe, December 2012'.

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