[Study on the genome sequence of influenza virus subtype A/H3N2 strains circulated in Zhejiang province during 1998 to 2009].

OBJECTIVE: To analyze the relationship between influenza epidemic and genetic characteristic on the whole genome of influenza virus subtype A/H3N2 strains isolated in Zhejiang province during 1998 to 2009. METHODS: All of the eight genes from the 19 Zhejiang influenza virus isolates, circulated during 1998 to 2009, were amplified by RT-PCR and sequenced. The obtained sequences were aligned and analyzed with the vaccine strains being used in the last 10 years. RESULTS: The highest mutation happened within HA and NA genes and the amino acid divergent ratios were 13.98% and 10.00%. Amongst the six internal proteins, the amino acid divergent ratios of NP, M2 and NS1 were 6.43%, 6.19% and 3.48% respectively, and the others were lower than 3%. Other than the HA and NA genes, mutations were also observed on six internal genes of the strains isolated in those years when the influenza virus subtype A/H3N2 was widely circulating. Additionally, there had been an obvious genetic lag between vaccine strains recommended by WHO and the contemporary Zhejiang epidemic strains for many years. CONCLUSION: Besides on HA and NA genes, surveillance programs should also be covered mutations regarding the internal genes of influenza virus subtype A/H3N2 strains, in order to provide important information for forecasting and warning of a new round of influenza epidemic.