EuroFlu: New H1N1 (2009) genetic subgroup characterized by S185T substitution in the HA detected, A/England/142/2010.

[Giuseppe]

Source: EuroFlu, http://www.euroflu.org/cgi-files/bulletin_v2.cgi

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Based on the genetic characterization of 165 influenza viruses,

• 90 belonged to the pandemic A/California/7/2009 A(H1N1) clade;
  
• 4 belonged to the pandemic A/Christchurch/16/2010 A(H1) clade;
• 23 belonged to the pandemic A/Hong Kong/2213/2010 A(H1) clade;
• 16 were reported as A(H1) pandemic not attributed to group category but belonging to the recently emerged A/England/142/2010 subgroup characterized by S185T substitution in the HA;
• 5 belonged to the A(H3) clade represented by A/Perth/16/2009;
• 2 belonged to the A(H3) clade represented by A/Victoria/208/2009;
• 17 belonged to the subgroup represented by A/Hong Kong/2121/2010 in the A/Victoria/208/2009 A(H3) clade;
• 7 belonged to the B/Bangladesh/3333/2007 clade (Yamagata lineage), and
• 1 to the B/Brisbane/60/2008 clade (Victoria lineage).

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Since the genetic characterization algorithms were put in place for pandemic influenza A(H1N1) viruses at the start of the 2010/2011 influenza season, a new genetic subgroup has been observed to emerge that is geographically dispersed and increasing in prevalence.

This genetic subgroup is characterized by an S185T substitution in HA and is represented by A/England/142/2010.

To date, viruses carrying the S185T substitution remain antigenically similar to the current vaccine virus A/California/7/2009.

At present, 98% of antigenically characterized viruses from the 2010/2011 influenza season are similar to the viruses included in the 2010/2011 northern hemisphere influenza vaccines.

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