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Paradigm Shift Intervention Monitoring
Frequent H1N1 M Gene Acquisitions In North
The above comments are from a recent paper, “Multiple Reassortment between Pandemic (H1N1) 2009 and Endemic Influenza Viruses in Pigs, United States”, which found 7 different influenza gene constellations in Northn American swine, all of which had the M gene segment from pandemic H1N1, raising concerns that this acquisition offers a selection advantage. The author speculated that this selection may be related to transmission.
Another recent paper used a guinea pig model to demonstrate increased transmission in isolates with an H1N1 M gene raising concerns that the widespread acquisition of the pandemic H1N1 M gene segment would lead to increased transmission of trH3N2 in humans.
This concern was increased by the recently released sequences from a trH3N2 case in Indiana, A/Indiana/08/2011, which was a trH3N2 closely related with recent trH3N2 human cases, but had acquired a pandemic H1N1 M gene. The early MMWR released on Friday described two recent trH3N2 cases, and both had a pandemic H1N1 M gene segment with seven trH3N2 swine gene segments, a constellation not reported previously.
The appearance of the pandemic H1N1 M gene in two trH3N2 recent cases that were not epidemiologically linked, raises concerns that this constellation is transmitting in humans. The recent case from Pennsylvania was linked to a recent fair in Washington County. Symptomatic attendees are being tested for evidence of a trH3N2 infection.
Release of the sequence from Pennsylvania as well as an update on the number of symptomatic attendees under investigation would be useful.