Prevalence of sexually acquired hepatitis C virus (HCV) infection in sexually transmitted infection (STI) patients

Objectives: Hepatitis C virus (HCV) is commonly contracted through parenteral exposures such as needle-sharing in injection drug users (IDU) and transfusion of contaminated blood. As the significance of sexual transmission of HCV remains controversial, this study was designed to examine its prevalence in sexually transmitted infections (STI) patients, the latter considered as a surrogate of sexually active individuals who have engaged in unsafe sex. Methods: A cross-sectional study was conducted in Hong Kong at the Social Hygiene Service which operates STI clinics in the public sector. Over a 3-month period, all adult patients attending two major clinics were invited to have a blood test for HCV antibody (anti-HCV). Positive results were investigated afterwards by RNA testing, genotyping and phylogenetic analysis, coupled with their correlation with clinical histories. Results: Totally 959 STI clinic attendees were screened. Six were anti-HCV positive, giving an overall HCV prevalence of 0.6%. Four were ex-IDU with HCV genotype 6 alpha, the same molecular identity of virus in IDU in Hong Kong. One RNA negative patient had probably contracted the virus via tattooing. An HIV co-infected patient with secondary syphilis had HCV genotype 3 alpha that clustered with those of HIV-infected men who have sex with men (MSM) in Hong Kong. Conclusion: The risk of HCV transmission through sexual contacts in the community remains low. Its occurrence in MSM and the setting of HIV co-infection is however a cause for concern.