MOLECULAR EPIDEMIOLOGY OF HEPATITIS-C IN AUSTRALIA

The aim of this study was to determine the distribution of hepatitis C virus (HCV) genotypes in Australian patients with hepatitis C and to identify factors associated with particular genotypes. Serum isolates of HCV-RNA were genotyped using a commercial oligonucleotide hybridiza tion (line probe) assay. Relationships between demographic factors, mo de of HCV transmission and HCV genotype were assessed by logistic regr ession analysis. Among 463 patients with hepatitis C, 425 tested posit ive for HCV-RNA and a single HCV genotype was identified in 420 cases. The patients' places of birth were Australia or New Zealand (62%), As ia (13%), Europe (12%), Mediterranean (6%), Middle East (6%) and other countries (< 1%). The most common genotypes were type 1 (52%) or type 3 (32%); type 2 (9.3%), type 4 (5.5%) and type 6 (1.7%) were less com mon. Patients with genotype Ib were older (48 +/- 13 years, P<0.001) a nd patients with genotype 9 were younger than the remaining patients ( 37 +/- 11 years vs 42 +/- 12 years, P<0.001). Among type 1 isolates, I b was more common for patients born outside Australia compared with th ose born in Australia (50% vs 13%, P<0.001) whereas non-1b subtypes we re more common among Australian-born patients. Likewise, 21 of 23 (91% ) patients with type 4 were from Egypt and six of seven (86%) with typ e 6 were from Vietnam. The relative importance of parenteral risk fact ors for HCV also varied according to geographic origin. Thus, a defini te risk. factor for HCV acquisition was identified in > 95 % of Austra lian-born patients, but in only 33% of Asian or Mediterranean-born pat ients. Logistic regression analysis indicated that region of birth and risk factor (intravenous drug use or not) would allow 98% of type 4 c ases and 76% of type Ib cases to be identified correctly. In summary, region of birth, patterns of migration over time and risk factors for transmission of HCV interact to determine the distribution of HCV geno types in a multi-racial community like Australia.