High prevalence of hepatitis C virus genotype 6 among certain risk groups in Hong Kong.

The genotype of hepatitis C virus (HCV) of 172 HCV-RNA positive serum specimens taken from patients with chronic liver diseases, thalassaemia major, chronic renal failure (CRF), haemophilia and intravenous drug abusers (IVDA) was determined by analysis of the amplified 5'UTR region by genotype-specific oligonucleotide probes and restriction fragment length polymorphism (RFLP). Six different genotypes and subtypes (1a, lb, 2, 3, 4 and 6) were found. Genotype lb was the predominant genotype among patients with chronic liver diseases (69.6%), followed by genotype 6 (18.8%), which was similar to that reported for blood donors in earlier studies. Pronounced differences in the distribution of genotypes were seen between the four risk groups. Patients with CRF had a similar distribution to those with chronic liver diseases, whilst the greatest diversity of genotypes was seen in patients with haemophilia, which was expected since they were given factor VIII manufactured overseas. Genotype 6 was particularly prominent in patients with thalassaemia major (50%) and IVDA (62.5%). It is possible that clonal spread of HCV genotype 6 has taken place among a closed subset of the population in Hong Kong through intravenous drug abuse.