Influenza A(H1N1)pdm, influenza A(H3N2), and influenza B/Victoria/2/87 lineage viruses have been characterised genetically and antigenically.

• Recently isolated A(H1N1)pdm viruses continue to fall into several genetic groups but all groups show antigenic similarity to the currently recommended vaccine virus A/California/7/2009.
• A(H3N2) viruses also continue to fall into distinct genetic groups with some viruses showing antigenic difference from the currently used vaccine virus A/Perth/16/2009, but there is no consistent correlation of altered antigenicity with any genetic group.
• Influenza B viruses of the B/Victoria/2/87 lineage have predominated over those of the B/Yamagata/2/87 lineage. Most of the B/Victoria/2/87 lineage viruses are genetically and antigenically similar to the currently recommended vaccine virus B/Brisbane/60/2008.