Molecular Characterization of Hemagglution Gene of Influenza A/H3N2 Virus and Results of Pathogenic Monitoring of Influenza in Chenzhou in 2007

Objective To analyze the epidemic situation and the distribution of types of influenza virus, and to know the molecular characterization of influenza A (H3N2) virus in prevalence in Chenzhou in 2007. Methods The throat swab specimens were collected from cases with influenza-like illness (ILI) in influenza monitoring hospitals. Influenza virus was isolated with MDCK cells and then identified by HA and HI methods. 4 strains of influenza A (H3N2) virus were isolated form sentinel hospitals, and hemagglutination genes of 4 strains were amplified by RT-PCR. The products were purified and sequenced. Results A total of 1,435 specimens were tested, and 277 influenza virus stains were isolated. The positive rate was 19.30%. 156 stains of A (H3N2) influenza virus were isolated. As compared with the northern hemisphere vaccine strain A/Wisconsin/67/05 in 2007, the variation sites of influenza strains isolated occurred. Conclusions Influenza A (H3N2) virus was the predominant epidemic strain in Chenzhou in 2007. HA1 gene variation of influenza A (H3N2) virus in Chenzhou in 2007 was recorded, which suggested it was the main cause leading to the spread of influenza.