November 25, 2011
Emergence of New Human Contagion trH3N2
Posted by: admin : Category: Flu vaccine
The acquisition of the M gene likely occurred as a result of swine being co–infected with the swine influenza A (H3N2) virus and the human 2009 H1N1 virus. While we know the M gene plays a role in influenza virus infection, assembly and replication, the significance of this change in these swine–origin influenza A (H3N2) viruses is unknown at this time. CDC continues to investigate the implications of this genetic change.
The 2011 trH3N2 human sequences extended the spread of the 2010 human trH3N2 sequences by retaining 5 of the 8 gene segments. The new contagion has swapped out the other three gene segments, PB1, NA, MP for genes found in earlier human triple reassortants (trH1N1, trH3N2, pandemic H1N1), to make a new human contagion, trH3N2, that can efficiently transmit in humans. As has been mentioned by the CDC and WHO, the 2011 human trH3N2 sequences have bought a pandemic H1N1 M gene segment, which is critical for the efficient transmission of pandemic H1N1 between humans.
This acquisition would lead to more efficient transmission of trH3N2 which bought the M segment from pandemic H1N1. The isolate from the patient in Indiana, A/Indiana/08/2011, has genes that are closely related to the genes of early human cases with trH3N2, but it has also bought the H1N1 MP gene segment. 
These cases increase the Pennsylvania total of confirmed cases to five, including three 2011 cases with the M gene segment. The three confirmed cases represents the largest number of confirmed trH3N2 cases at a given location, and the investigation is still ongoing.
