Distribution and diversity of hepatitis B virus genotypes in Yunnan, China

Hepatitis B virus (HBV) is one of the most prevalent pathogens in the world, and infection with this virus is a serious threat for public health. Yunnan is considered as an important endemic center for blood-borne viruses such as human immunodeficiency virus and hepatitis C virus, in China. However, the distribution and diversity of HBV subgenotypes remain unclear in Yunnan province. In the current study, HBV positive samples were collected from different prefectures of Yunnan province and their molecular epidemiological characters were determined. Phylogenetic analysis on the pre-S/S gene (865 bps) showed the prevalence of four HBV genotypes, including genotype B (24 cases, 33.3%), genotype C (45 cases, 62.5%), genotype I (two cases, 2.78%) and C/D recombinants (one case, 1.39%). The most prevalent genotypes B and C could be sub classified into subgenotype B2 and C1, C2, C5, and C7, respectively. Clusters of subgenotype B2 and C2 consisted of strains from China and other East Asian countries, while subgenotype C1, C5, and C7 and genotype I formed a cluster together with strains from Southeast Asia. Using Bayesian inference from phylogenetic, HBV genotypes B and C were estimated to have originated in 1860s and 1910s with an evolutionary rate of 3.26 and 8.01 × 10(-4) substitutions/site/year, respectively. These findings indicate that the distribution of HBV genotypes in Yunnan was influenced by strains from the rest of China and the neighboring countries.