Available online at www.sciencedirect.com Drug and Alcohol Dependence 91 (2007) 228–235 Modelling the hepatitis C virus epidemic in Australia Karina Razali a,* , Hla Hla Thein a , Jane Bell b , Mark Cooper-Stanbury c , Kate Dolan d , Greg Dore a , Jacob George e , John Kaldor a , Maria Karvelas f , Jiong Li a , Lisa Maher a , Sharyn McGregor b , Margaret Hellard g , Fiona Poeder h , Julianne Quaine b , Kim Stewart i , Helen Tyrrell j , Martin Weltman k , Owen Westcott i , Alex Wodak l , Matthew Law a a National Centre in HIV Epidemiology and Clinical Research, University of New South Wales, Sydney, NSW 2010, Australia b Department of Health and Ageing, Canberra, ACT 2601, Australia c Australian Institute of Health and Welfare, Canberra, ACT 2617, Australia d National Drug and Alcohol Research Centre, University of New South Wales, Sydney, NSW 2052, Australia e Westmead Millenium Institute, Westmead, NSW 2145, Australia f Victorian Government Department of Human Services, Melbourne, VIC 3000, Australia g Burnet Institute, Melbourne, VIC 3001, Australia h Australian Injecting and Illicit Drug Users League Inc., Canberra, ACT 2600, Australia i NSW Health, North Sydney, NSW 2060, Australia j Australian Hepatitis Council, Woden, ACT 2606, Australia k Nepean Hospital, University of Sydney, Sydney, NSW 2006, Australia l Alcohol and Drug Service, St Vincent’s Hospital, Sydney, NSW 2010, Australia Received 13 December 2006; received in revised form 30 May 2007; accepted 30 May 2007 Abstract Background: Hepatitis C virus (HCV) infection in Australia is predominantly transmitted through injecting drug use. A reduction in the heroin supply in Australia in late 2000 and early 2001 may have impacted the number of injecting drug users (IDUs) and consequently the number of new hepatitis C infections in Australia. This paper updates estimates of HCV incidence and prevalence between 1960 and 2005. Methods: Simple mathematical models were used to estimate HCV incidence among IDUs, migrants to Australia from high HCV-prevalence countries, and other HCV exposure groups. Recent trends in numbers of IDUs were based on indicators of injecting drug use. A natural history of HCV model was applied to estimate the prevalence of HCV in the population. Results: The modelled best estimate of past HCV incidence showed a consistent increasing rate of HCV infections to a peak of 14,000 new seroconversions in 1999, followed by a decline in 2001–2002 coincident with the decline in heroin availability. HCV incidence was estimated to be 9700 (lower and upper limits of 6600 and 13,200) in 2005. Of these, 88.7% were estimated to be through injecting drug use, 7.2% among migrants and 4.1% through other transmission routes. An estimated 264,000 (lower and upper limits of 206,000 and 318,000) people were HCV antibody positive in 2005. Conclusions: Mathematical models suggest that HCV incidence in Australia decreased from a peak of 14,000 new infections in 1999 to 9700 new infections in 2005, largely attributable to a reduction in injecting drug use. The numbers of people living with HCV in Australia is, however, estimated to continue to increase. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Hepatitis C virus; Australia; Mathematical models; Epidemic; Injecting drug use * Corresponding author. Tel.: +61 2 93825 0900; fax: +61 2 9385 0920. E-mail address: krazali@nchecr.unsw.edu.au (K. Razali). 1. Introduction The prevalence of hepatitis C virus (HCV) infection world- wide has been estimated to be about 3% with 170 million people affected (Sy and Jamal, 2006). The prevalence was estimated to be 3.9 million people in the United States (US), and about 0376-8716/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.drugalcdep.2007.05.026