Selection pressure analysis of H3N2 influenza virus from China between 1992 and 2012

Objective In order to investigate the relationship between selection pressure and the prevalence of antigenic clusters,we sequenced and analyzed the H3N2 influenza virus from China between 1992 and 2012.Methods The H3N2 influenza virus (n =1206) in China from 1992 to 2012 was analyzed,include global selection pressure and sites positive selection pressure analysis.Results Considering all the H3N2 influenza viruses during these 21 years,a total of four amino acid sites subject to positive selection.The global selection pressure varies with the variation of different antigenic clusters and three years with peak bottom selection pressure were identified.Conclusion The global selection pressure rise from the peak bottom,a new antigenic clusters will appear and prevalent in the population,indicating the best time to replace the vaccine strain. Key words: Influenza B virus;  Selection(Genetics)