Hepatitis C virus genotypes in Australia.

The relative distribution of Australian hepatitis C virus (HCV) genotypes was determined for 500 isolates. Genotyping was performed using a commercial reverse phase hybridization assay after amplification of the 5' untranslated region of HCV by the polymerase chain reaction. Australian isolates comprised, predominantly, genotype 1 (55%) and genotype 3 (38%) with genotype 2 accounting for only 7%. Genotype 3a was the most common subtype. When the major risk groups of injecting drug users or transfusion-acquired hepatitis C were compared, there was a significantly higher incidence of genotype 1b in the transfusion-acquired group (P < 0.03). When the age of the patients was analysed, genotype 3a was more prevalent in the 21-40-year age group than the 41-60-year age group (P < 0.05). There was no significant difference in genotype distribution between males and females. HCV genotypes 1, 2 and 3 are most often found in developed countries but the relatively high prevalence of genotype 3a in Australia is unusual.