Hepatitis C infection in injection drug users from southern China: Low viral clearance, multiple genotypes and mixed genotype infections

Hepatitis C virus (HCV) affects over 170 million persons worldwide. After acute infection the majority of individuals become chronically infected with HCV. Over time this can lead to cirrhosis, hepatocellular carcinoma and end-stage liver disease. The majority of new HCV infections are occurring in injection drug users (IDUs) and in parts of the world where HCV treatments are not available. In a cohort of heroin users from Guangxi Province, southern China, HCV is rapidly spreading through injection drug use as new heroin users quickly change from smoking to injection. IDUs from southern China rarely undergo spontaneous viral clearance of HCV, resulting in a very high level of chronic infections. Hepatitis B virus (HBV) co-infection and a shorter length of injection drug use were found more often in the few IDUs who were able to clear HCV. A high level of genotype diversity is present throughout the province with the following genotypes present: 1a, 1b, 3a, 3b, 6a and 6e. Within genotypes there is very little nucleotide variation between different study sites, within the province or by human immunodeficiency virus (HIV) serostatus. This suggests that like the current HIV epidemic in the province, the HCV epidemic began with a few isolates and has been rapidly spreading in IDUs throughout the province. IDUs are repeated exposed to HCV through unsafe injection practices. In this cohort repeated exposures have led to re-infection with heterologous HCV genotypes in cleared individuals. Repeated exposures have resulted in mixed genotype infections in re-infections and also during acute infections. Individuals with mixed genotype infections may be less likely to clear their infections than individuals with a single genotype infection. These finding suggest the consequences of repeated exposures to HCV through injection drug use may be responsible for the high level of chronic infections seen in this population.