A Molecular Epidemiological Research On Hepatitis C Virus Infection Among Intravenous Drug Users In Yunnan Province

Hepatitis C is an important infectious disease which threatens people’s health. Approximately170million people are infected with the hepatitis C virus (HCV) worldwide. The overall prevalence of HCV in China is3.2%. HCV infections progress easily to chronic hepatitis. Twenty to thirty percent of HCV infections lead to liver cirrhosis and hepatocellular carcinoma and end stage liver disease.During replication of HCV, RNA-dependent RNA polymerase (RdRp) frequently introduces random nucleotide errors, which results in relatively high rate of spontaneous nucleotide substitutions. HCV can be divided into6major genotypes and each genotype has several subtypes. HCV genotype or subtype may impact its pathogenicity and responses to treatment directly.Recently, high proportions (15.6%-98.7%) of intravenous drug users (IDUs) in China were found to be positive for hepatitis C virus (HCV). Yunnan Province is located in southwestern China and borders one of the world’s most important opium-producing regions, thus it is an important drug trafficking route to other regions of China. The prevalence of HCV infection among IDUs was about80%. Here, we assessed100HCV-positive plasma samples from IDUs who were enrolled through the Kunming Center for Disease Control and Prevention in2012. HCV C/E1fragments were PCR-amplified and T-A cloned, then sequenced by the Beijing Genomics Institute. We identified eight HCV subtypes (1a,1b,3a,3b,6a,6n,6u and6v), of which genotype6was most predominant (frequency,47%) followed by genotypes3(41%) and1(12%). HCV subtypes6n (30%) and3b (29%) were most common and were identified in59%of the IDUs. We compared HCV genotypes among IDUs in Yunnan Province with those from other regions and found that the distribution patterns of HCV genotypes in Yunnan Province were similar to those in southern China, but different from those in eastern China. However, the distribution patterns of HCV subtypes varied among Yunnan Province and southern China, despite the shared similar genotypes. A comparison of the current data with those previously reported showed that the frequency of HCV genotype6increased from25%to47%within5years, especially subtypes6a (5%to15%) and6n (11.2%to30%). In contrast, the frequencies of subtypes3a and1b decreased by almost50%within5years. Our results provided further information to support the assertion that drug trafficking routes influence HCV transmission patterns among IDUs in Yunnan Province. The frequency of HCV genotypes and subtypes changed rapidly among IDUs in Yunnan Province and subtypes6a and6n may have originated in Vietnam and Myanmar, respectively.