The HA gene sequence analysis of an influenza A(H1N1) viral strain isolated from the first mortality case in Jinhua,Zhejiang

Objective To analyze the hemagglutinin(HA) gene sequence of an influenza A(H1N1) virus strain isolated from the first mortality case in Jinhua.Methods The H1N1 influenza virus was isolated with MDCK cells and confirmed with the real-time RT-PCR assay.The PCR products of HA gene were sequenced and a phylogenetic tree was generated with the correlated sequences from GeneBank.Results The strain of influenza A/H1N1 virus was isolated from all 3 throat swab specimens of an influenza suspect mortality case.Unfortunately,the virus was the first strain of influenza A/H1N1 confirmed in Jinhua in 2009.The phylogenetic tree demonstrated that the HA gene sequence of the new virus was highly homologous with the sequence of worldwide circulated influenza H1N1 virus in 2009.The strain was more closely related to classical swine influenza virus than swine or avian influenza A/H1N1 virus isolated in Europe and Asia.Conclusion The isolated influenza A/H1N1 virus was similar to the 2009 pandemic strain of influenza virus as well as the influenza A/H1N1 vaccine strain candidate,which was later recommended by WHO.