Human trH3N2 Matches Human trH1N1Huron Ohio Cluster
Recombinomics Commentary 19:10
November 15, 2010

An H1N1 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.

The above comments describe the largest triple reassortant outbreak reported to date, other than the 2009 pandemic.  That outbreak involved H1N1, which was isolated from a presenter and her father as well as multiple swine at the 2007 Huron County fair.  However, influenza reassorts in swine, so the same internal proteins can be found in H3N2 isolates which have swapped H3 and N2 for H1 and N1.

The recent pager alert on two trH3N2 cases in the United States (Wisconsin and Pennsylvania) focused attention on the five reported cases.  All have been reported after the 2009 H1N1 pandemic and have raised concerns that they may signal an H3N2 swine flu pandemic. 
Sequences from the first outbreak, at a Riley Country fair, were released (A/Kansas/13/2009), but sequences from the five subsequent cases have not been released.  However, two years earlier there was a large outbreak at a Huron County fair in Ohio.  trH1N1 was isolated from a presenter (10F) and her father (36M) and the HA sequences (A/Ohio/01/2007 and A/Ohio/02/2007) were released.  The two sequences matched each other as well as trH1N1 HA sequences isolated from swine at the fair (A/swine/Ohio/24366/07 and A/swine/OH/511445/2007).  Full sequences from the swine were made public, and the internal genes such as PB2, PB1, and PA were closely related to the sequences from Kansas/13/2009 (see list here and here and here).

The conservation of these sequences and linkage to human trH1N1 and trH3N2 cases raise pandemic concerns.

Recombinomics Presentations

Recombinomics Publications

Recombinomics Paper at Nature Precedings