Evolutionary characteristics and immune mutation of hepatitis C virus genotype 1b among intravenous drug users in mainland, China.

China is one of the countries with the heaviest burden of hepatitis C virus (HCV) worldwide, especially subtype 1b. To better control hepatitis C, insights into the characteristics of dynamic spread and genomic mutations are urgently needed. We retrieved sequences of HCV-1b NS5B among intravenous drug users (IDUs) and general people (Non-IDUs) in China from 2000 to 2011 in NCBI. Bayesian phylogenetic and phylogeographic analyses were used to evaluate the transmission dynamics of HCV-1b. Non-synonymous substitutions were detected to illustrate immune adaptation. Evolutionary history demonstrated that HCV-1b effective population size experienced a sharp increase in 1990. HCV-1b sequences among IDUs had a higher estimated evolutionary rate (5.7185 × 10-3  substitutions/site/year) than overall (7.7332 × 10-4 ). 105/136 (77.2%) of HCV-1b sequences clustered into 38 networks. The average non-synonymous HCV-1b immune epitopes among IDUs were 0.211, higher than non-IDUs, especially in the HLA-A*02 molecular recognition region. All of these posed significant challenges for the prevention and treatment of HCV. Heterogeneity and genetic linkages of HCV-1b suggest that evolutionary surveillance of HCV in cities in east-central China and among IDUs could not be neglected.