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Paradigm Shift Intervention Monitoring
trH3N2 and Huron Ohio Fair trH1N1 Clusters Linked
influenza A virus, A/swine/Ohio/24366/07, was isolated from pigs in an
Ohio county fair. Twenty-six people who came in contact with the
infected pigs developed respiratory disease and two of these people
were laboratory confirmed as H1N1 by the Centers for Disease Control
and Prevention (CDC). The A/swine/Ohio/24366/07 virus we isolated from
swine was shown at the CDC to have 100% identical genome sequence to
the human virus associated with the county fair.
These internal genes are closely related to genes found in human H3N2 triple reassortants (trH3N2), as well as swine H1N1 triple reassortants currently circulation such as A/swine/Minnesota/A01047613/2010 which was isolated from a sample collected December 10, 2010.
The PB2 gene is virtually identical to the sequence from the index case (31M) in the Minnesota cluster (A.Minnesota/11/2010) and pandemic H3N2 vaccine target, which is also almost identical to two other recent human isolates, A/Wisconsin/12/2010 and A/Pennsylvania/40/2010 (see list here). The NS genes between all four 2010 isolates are identical, and closely related to the 2007 human isolates from the Huron County fair (see list here).
The similarities extend to the other recent H3N2 triple reassortant, indicating this phylogenetic clustering is linked to the targeting of human cases and the cluster described above for the Ohio fair and the familial cluster in Minnesota raise serious concerns that the number of human trH3N2 cases is markedly higher than those reported.