Genome evolution of novel influenza A (H1N1) viruses in humans

The epidemic situation of A H1N1 flu arose in North America in April 2009,which rapidly expanded to three continents of Europe,Asia and Africa,with the risk ranking up to 5.Until May 13th,the flu virus of A H1N1 had spread into 33 countries and regions,with a laboratory confirmed case number of 5728,including 61 deaths.Based on IRV and EpiFluDB database,425 parts of A H1N1 flu virus sequence were achieved,followed by sequenced comparison and evolution analysis.The results showed that the current predominant A H1N1 flu virus was a kind of triple reassortment A flu virus:(i) HA,NA,MP,NP and NS originated from swine influenza virus;PB2 and PA originated from bird influenza virus;PB1 originated from human influenza virus.(ii) The origin of swine influenza virus could be subdivided as follows:HA,NP and NS originated from classic swine influenza virus of H1N1 subtype;NA and MP originated from bird origin swine influenza virus of H1N1 subtype.(iii) A H1N1 flu virus experienced no significant mutation during the epidemic spread,accompanied with no reassortment of the virus genome.In the paper,the region of the representative strains for sequence analysis(A/California/04/2009(H1N1) and A/Mexico/4486/2009(H1N1)) included USA and Mexico and was relatively wide,which suggested that the analysis results were convincing.