Friday, August 02, 2013

ECDC: Influenza Virus Characterization – July 2013


Photo Credit NIAID



# 7537



As summer moves inexorably towards fall, those of us in the northern hemisphere begin to think about the upcoming flu season, and just how good of a match this year’s flu vaccine will turn out to be.


It requires 6 months of lead time to develop, manufacture, and distribute the yearly seasonal influenza vaccine. During that time it is possible that the strains in circulation can drift antigenically (or change completely) from the strains selected last February for the vaccine.


NIAID has a terrific 3-minute video that shows how influenza viruses drift over time, and why the flu shot must be frequently updated, which you can view at this link.

So we watch surveillance reports - like those coming from the CDC’s FluView and the ECDC’s  monthly Virus characterization reports – for any signs that there’s a `new flu’ in town.


Today, the ECDC released their latest Influenza Virus Characterization report (for July 2013).


While antigenic changes continue to show up in both influenza A/H1N1 and A/H3N2, the good news is – the majority of the viruses being analyzed still appear to be antigenically similar to those in this year’s vaccine. The influenza B vaccine strain also appears to be a good match for the bulk of the B viruses tested.


This year, you can get a little added protection, as  a new quadrivalent (4 strain) vaccine will be available which can help protect you against both (Yamagata & Victoria) influenza B strains.


This Abstract from the ECDC, follow the link to read the entire report.



Influenza Virus Characterisation, July 2013

Surveillance reports - 02 Aug 2013

Available as PDF in the following languages:

This document is free of charge.


In the course of the 2012–13 season, A(H1N1)pdm09, A(H3N2) and B/Victoria- and B/Yamagata-lineage influenza viruses have co-circulated in ECDC-affiliated countries over what was an extended influenza season. The relative prevalences of each virus type/subtype has varied between countries.

• Type A and type B viruses have been detected in similar proportions but with type A peaking and declining slightly before type B.

• A(H1N1)pdm09 viruses have been detected at approximately twice the level of A(H3N2) viruses.

• The vast majority of A(H1N1)pdm09 viruses have remained antigenically similar to the vaccine virus, A/California/07/2009, but continued to show genetic drift with an increasing prevalence of genetic group 6 viruses.

• The vast majority of A(H3N2) viruses have been antigenically and genetically similar to cell-propagated A/Victoria/361/2011, a genetic group 3C virus and the prototype vaccine virus for the 2012–13 influenza season; group 3C viruses have circulated exclusively in recent months and the recommended vaccine virus for the 2013–14 season, A/Texas/50/2012, is in this genetic group.

• Viruses of the B/Yamagata-lineage have predominated over those of the B/Victoria-lineage.

• B/Victoria-lineage viruses have remained antigenically similar to cell-propagated reference viruses of the B/Brisbane/60/2008 genetic clade.

• B/Yamagata-lineage viruses formed two antigenically distinguishable genetic clades: clade 3 represented by B/Wisconsin/1/2010 (the recommended vaccine component for the 2012–13 influenza season) and, in increasing numbers, clade 2 represented by B/Massachusetts/2/2012 (the recommended vaccine component for the 2013–14 influenza season).

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