Hepatitis C Virus Subtypes Novel 6g-Related Subtype and 6w Could Be Indigenous in Southern Taiwan with Characteristic Geographic Distribution.

Hepatitis C virus (HCV) genotype (GT) 6 is the most genetically diverse GT and mainly distributed in Southeast Asia and south China but not Taiwan. Earlier studies showed the major HCV GTs in Taiwan were GT 1b and 2 with very rare GT 6 except in injection drug users (IDUs), and subtype 6a is the main GT 6 subtype among IDUs. Recently, we reported a much higher prevalence (18.3%) of GT 6 in Tainan City, southern Taiwan. This study was designed to clarify the subtypes of GT 6 in this endemic area. A total of 3022 (1343 men and 1679 women) HCV viremic patients were enrolled. Subtypes of GT 6 were determined by sequencing of core/E1 and nonstructural protein 5B in 322 of 518 GT 6 patients. The overall GT 6 prevalence rate was 17.1% (518/3022), with higher prevalence districts (>25%) located in northern Tainan. A novel 6g-related subtype is the most prevalent subtype (81.0%), followed by 6w (10.8%), 6a (7.5%), and 6n (0.7%). The high GT 6 prevalence in Tainan was mainly due to a novel 6g-related subtype and 6w. These two subtypes could be indigenous in Tainan with characteristic geographic distribution.

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.

High prevalence of genotype 6 hepatitis C virus infection in Southern Taiwan using Abbott genotype assays.

BACKGROUND/PURPOSE: Abbott RealTime Genotype II assay can effectively identify hepatitis C virus (HCV) genotypes (GTs), but some GT 6 subtypes might not be differentiated from GT 1. Abbott RealTime Genotype II PLUS and sequencing might be needed to resolve these ambiguous results. Unlike the high prevalence of GT 6 in Southeast Asia, GT 6 had rarely been reported in Taiwan except in intravenous drug abusers (IDU). But the prevalence of GT 6 in Taiwan might be underestimated. We conducted this study to determine the GTs in a HCV endemic area in Southern Taiwan. METHODS: A total of 1147 patients with hepatitis C viremia for direct acting antivirals (DAA) treatment at the Chi Mei medical system in Tainan were enrolled. Genotype was determined using a working flow consisted of Abbott GT II, PLUS assays and 5' untranslated region (5' UTR)/core sequencing. RESULTS: Among the 1147 patients, 883 (77.0%) obtained GT results by GT II, 264 (23.0%) samples with ambiguous results by GT II assay received further tests, including 194 (73.5%) with PLUS assay and 70 (26.5%) with 5'UTR/core sequencing. Nearly three-quarters (73.5%) of ambiguous results by GT II assay were GT 6. Overall, 18.3% of samples were GT 6. Phylogenetic study of 11 samples of GT 6 subtypes showed 7 (63.6%) were 6 g. CONCLUSION: GT 6 is the major factor for high ambiguous rate by GT II. Unexpected high prevalence of GT 6 (18.3%) in Southern Taiwan, especially subtype 6 g, closely related to Indonesian strains, is first reported.