[Genetic Diversity and Evolution of the M Gene of Human Influenza A Viruses from 2009 to 2013 in Hangzhou, China].

We investigated the genetic diversity and evolution of the M gene of human influenza A viruses in Hangzhou(Zhejiang province,China)from 2009 to 2013,including subtypes of A(H1N1)pdm09strains and seasonal A(H3N2)strains.Subtypes of analyzed viruses were identified by cell culture and real-time reverse transcription-polymerase chain reaction,followed by cloning,sequencing and phylogenetic analyses of the M gene.Assessment of 5675 throat swabs revealed apositive rate for the influenza virus of 20.46%,and 827 cases were diagnosed as infections due to influenza A viruses.Seventy-six influenza-A strains were selected randomly from nine stages during six phases of a virus epidemic.Sequences of the M gene showed high homology among six epidemics with identities of amino-acid sequences of 98.98-100%.All strains contained the adamantine-resistant mutation S31 Nin its M2 protein.Two of the A(H1N1)pdm09strains had double mutants of V27A/S31 N or V27I/S31 N.One of the seasonal A(H3N2)viruses had another form of double-mutant R45H/S31 N.Evolutionary rate of the M gene was much lower than that of the HA gene and NA gene.Compared with A(H3N2)strains,higher positive pressure on the M1 and M2proteins of A(H1N1)pdm09viruses was observed.Separate analyses of M1 and M2proteins revealed very different selection pressures.Knowledge of the genetic diversity and evolution of the M gene of human influenza-A viruses will be valuable for the control and prevention of diseases.