Modelling the hepatitis C virus epidemic in Australia.
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.
National Centre in HIV Epidemiology and Clinical Research, University of New South Wales, Sydney, NSW 2010, Australia. krazali@nchecr.unsw.edu.au
Karina
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Razali
Hla Hla
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Thein
Jane
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Bell
Mark
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Cooper-Stanbury
Kate
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Dolan
Greg
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Dore
Jacob
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George
John
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Kaldor
Maria
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Karvelas
Jiong
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Li
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Maher
Sharyn
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McGregor
Margaret
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Hellard
Fiona
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Poeder
Julianne
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Quaine
Kim
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Stewart
Helen
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Tyrrell
Martin
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Weltman
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Westcott
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Wodak
Matthew
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Law
D000293:Adolescent; D001315:Australia / Q000453:epidemiology; D015897:Comorbidity; D018563:Disease Notification; D054242:Emigrants and Immigrants / Q000706:statistics & numerical data; D006526:Hepatitis C / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D015233:Models, Statistical; D018671:Needle-Exchange Programs; D015819:Substance Abuse, Intravenous / Q000453:epidemiology*; D019966:Substance-Related Disorders / Q000453:epidemiology / Q000517:prevention & control