Prevalence and genetic evolution of EA-H1N1 swine influenza virus in China

H1N1 swine influenza virus (SIV) has posed a potential threat to public health. Genetic evolution and amino acid substitutions of whole genome sequence of influenza virus have been shown to be associated with the virulence and pathogenicity of the virus. We made a statistical analysis of the prevalence of swine influenza virus in China and found that Eurasian avian-like H1N1 (EA-H1N1) SIVs were the main prevalent SIVs in China. We further analyzed the genotypes of EA-H1N1 SIVs, and the results showed that these viruses were divided into 11 genotypes, and there is an increasing number of reassorted EA-H1N1 SIVs in recent years, especially for those viruses whose viral genes PB2, PB1, PA and NP derived from pandemic H1N1/2009. Besides, we isolated a novel EA-H1N1 SIV (A/swine/Hubei/221/2006 (H1N1)). We find that this isolated virus is highly homologous to a previous human isolated EA-H1N1 virus A/Hunan/42443/2015 (H1N1). Taken together, this study analyzes the prevalence and genetic evolution of EA-H1N1 SIVs in China, which provides a theoretical basis for the prevention and control of swine flu.