An outbreak of HCV genotype 6a and 2a infection in South China: Confirmation of iatrogenic transmission by phylogenetic analysis of the NS5B region.

An outbreak of hepatitis C virus (HCV) infections, for which the risk factor was unknown, was previously identified in North Guangdong, China. In the present study, a total of 736 local residents were surveyed regarding their lifetime risk factors for HCV infection. Serum anti-HCV antibodies and HCV RNA were examined to confirm infection. In the HCV-positive samples, the core and nonstructural protein 5B sequences were amplified, and phylogenetic analysis was performed to determine the association between HCV subtypes and transmission routes. A total of 374 individuals were positive for anti-HCV antibodies. Blood transfusion, blood product transfusion, people who inject drugs and intravenous injection at a local clinic were identified as independent risk factors for HCV infection. Phylogenetic analysis revealed that the two predominant subtypes of HCV, 2a and 6a, were primarily focused in four homologous clusters. Patients with a history of intravenous injection at a local clinic were more likely to be found in the four clusters, compared with patients exposed to other risk factors. The present emergency retrospective survey showed a specific epidemiological feature of HCV infection in Zijin County and found genetic homology among individuals exposed to intravenous injection at a local clinic. Further evidence is required to confirm the causal association between the outbreak of HCV infection and intravenous injection.