[Source: European Centre for Disease Prevention and Control (ECDC), full page: (LINK).]
Influenza virus characterisation report for Europe: September to December 2013
10 Jan 2014
The latest issue of ECDC’s series on 'Influenza virus characterisation’ covers the time period since 1 September 2013.
Indicative of the late start of the 2013-14 influenza season, a low number of 46 influenza-positive specimens have been received from six EU/EEA countries so far in WHO Collaborating Centre for Reference and Research on Influenza in London.
Influenza type A viruses (91%) are dominating over type B (9%), as is often seen at the beginning of Northern Hemisphere influenza seasons. For type A, H3N2 viruses have been received in greater numbers than H1N1pdm09 viruses, with the ratio of 2:1.
The report further summarises the findings as follows:
- Compared to the 2012–13 influenza season where genetic subgroup 6C dominated among A(H1N1)pdm09 viruses, and based on the current global situation, genetic subgroup 6B viruses have been detected in increasing frequency. Subgroup 6B viruses have been antigenically similar to the vaccine virus, A/California/07/2009.
- Recently circulating A(H3N2) viruses have fallen within genetic subgroup 3C represented by the recommended vaccine virus for the 2013–14 season, A/Texas/50/2012; some new genetic clusters defined by specific HA amino acid substitutions have been observed for which antigenic characterisation is pending.
- No B/Victoria-lineage viruses have been received to date.
- Two genetic clades of B/Yamagata-lineage viruses continue to circulate: clade 3 represented by B/Wisconsin/1/2010 and clade 2 represented by B/Massachusetts/2/2012 (the recommended vaccine component for the 2013–14 influenza season). The great majority of recently circulating viruses fall within clade 2.
The report is prepared under ECDC framework contract and is based on analysis of influenza-positive specimens received by the MRC National Institute for Medical Research, the WHO Collaborating Centre for Reference and Research on Influenza in London.
For further details, download the complete report.