Seroprevalence and subtype distribution of hepatitis C virus among blood donors and intravenous drug users in northern/northeastern Thailand.

The prevalence of antibodies against hepatitis C virus (HCV) and the distribution pattern of HCV subtypes were analyzed among healthy blood donors and intravenous drug users (IVDUs) in northern/northeastern Thailand. The prevalence of anti-HCV antibodies was 3.2% (26/820) among blood donors in Khon Kaen, while it was 90% (71/79) among IVDUs in Chiang Rai. HCV RNA was detected in all anti-HCV-positive sera collected from blood donors and IVDUs tested, as determined by reverse transcription-PCR analysis. Sequence analyses of amplified fragments of the HCV genome revealed that in Khon Kaen and Chiang Rai, Thailand, HCV-3a (50-60%) was the most common HCV subtype, followed by HCV-1a, HCV-1b, and subtypes of clade 6, each at 10-20%.