Geographic variation of genotype 6 hepatitis C virus infection in an endemic area of southern Taiwan.

Taiwan is a hepatitis C virus (HCV) endemic country with geographic variation of prevalence and main genotypes(GTs) are 1 b and 2a. We recently reported high GT6 prevalence in Tainan of southern Taiwan. To clarify this special genotype as a local endemic disease and its geographic variation, the prevalence rates of HCV GTs of 37 districts of Tainan were analyzed. A total of 3040 patients with HCV viremia were enrolled. The prevalence rates of HCV GT 1a, 1 b, 2, 3, 4, 6 and mixed types were 3.9%, 31.6%, 45.9%, 0.6%, 0.2%, 17.1% and 0.5% respectively. GT6 prevalence showed marked variation from 0 to 39.2%. Four districts with GT6 prevalence >30% are located between Jishui and Zengwen rivers. Preliminary subtyping data were 6 g/a/w. This geographic variation with spatial restriction by two rivers with 6 g/w is suggestive of local endemic infection of preexisting GT 6 HCV for centuries.