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Paradigm Shift Intervention Monitoring
St Jude as released three full
sets of novel H1N2 from North Carolina (A/swine/North
Carolina/226126/2010) collected in September 8, 2010. The isolates
had a triple reassortant polymerase complex found in North American
swine (human PB1 and avian PA andPB2), but had pandemic H1N1 for the
other three internal genes (NP, MP, NS). The H1 was from seasonal H1N1
circa 2003, while the N2 was seasonal H3N2 circa 1996.
Thus, the novel H1N2 was a North American H1N2 triple reassortant that had replaced swine NP, MP, and NS with pandemic NP, MP, and NS. This new constellation of genes has much in common with reassortants from Argentina, England, and South Dakota. All have human H and N genes which have been circulating in local swine for 1-3 decades and all have replaced the three swine genes with three pandemic genes, which is matched with a polymerase complex with human PB1 and avian PA and PB2.
Thus, all 8 gene segments have a recent history of circulation in human hosts and therefore have the potential of jumping back to humans from swine. However, each of these jumps would introduce human flu genes that have been evolving in swine for decades.
These newly describe reassortants raise concerns that these flu genes will continue to evolve via recombination involving older human genes with newer swine genes leading to accelerated evolution.
In addition to the above reassortants, Hong Kong has released sequences from hundreds of Hong Kong isolates with receptor binding domain changes, including D225G, D225N, and D225E, in addition to S186P and S188N, as well as changes at position 156-159 including G158E. The circulation of these donor sequences in swine as well as the widespread reports of pandemic H1N1 in swine, continue to increase pandemic concerns.