BLOOD-BORNE VIRUS-INFECTIONS AMONG AUSTRALIAN INJECTING DRUG-USERS - IMPLICATIONS FOR SPREAD OF HIV

To describe the epidemiology of infection with hepatitis C virus (HCV) , hepatitis B virus (HBV) and human immunodeficiency virus (HIV) among injecting drug users (IDUs) in Australia, in relation to the potentia l for further spread of HIV in IDUs, a cross-sectional analysis was pe rformed on data from a sample of injecting drug users, correlating mar kers of exposure to blood-dome viruses with sex, age, sexual orientati on, primary current drug injected and duration of injecting in rural a nd metropolitan Victoria, Australia. The subjects were currently activ e IDUs from a wide spectrum of age, sex, sexual orientation, geographi cal location and social background, contacted and recruited through th eir social networks and from community agencies and prisons by trained peer workers who interviewed and collected blood from them in the fie ld. Sera were tested for antibody to HIV, HCV and hepatitis B core ant igen (HBcAg), for hepatitis B surface antigen (HBsAg), and for HCV RNA using reverse transcription and polymerase chain reaction (RT-PCR). A t entry to the study, 4.5% (14/311) had antibody to HIV, 47% (146/308) to HBcAg and 68% (206/303) to HCV. Prevalence of HBsAg was 1.8% overa ll (5/282), and 50% (84/168) were positive for HCV RNA. By multivariat e analysis, HIV seropositivity was strongly associated with a history of homosexual contact in males and with exposure to HBV but not to HCV . Those who reported their current primary injected drug to be ampheta mines were at greater and continuing risk of HIV infection than were c urrent heroin injectors, while the reverse applied for HCV. The differ ent patterns of exposure to different blood-borne viruses in this part icular population of IDUs probably reflects different interactions amo ng different social networks. HCV exposure provides a good surrogate m arker for risk behaviour among these IDUs, but HBV exposure provides a better marker for risk of HIV infection. More detailed surveillance s trategies for HIV infection; and more targeted HIV prevention programs are necessary to detect and to prevent further spread of HIV in these populations.