Modelling and calibration of the hepatitis C epidemic in Australia

Abstract

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 the number of new hepatitis C infections. This paper updates estimates of HCV incidence between 1960 and 2005 and models long-term sequelae from infection. Outcomes among those with HCV were also recently assessed in a linkage study assessing cancer and causes of death following HCV diagnosis in New South Wales. Linkage study outcomes have been used here to calibrate modelled outcomes. 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. Model predicted endpoints that were calibrated against the NSW linkage data over the period 1995—2002 were: (i) incident hepatocellular carcinoma (HCC); (ii) opioid overdose deaths; (iii) liver-related deaths; and (iv) all-cause mortality. Modelled estimates and the linkage data show reasonably good calibration for HCC cases and all-cause mortality. The estimated HCC incidence was increased from 70 cases in 1995 to 100 cases in 2002. All-cause mortality estimated at 1000 in 1995 increased to 1600 in 2002. Comparison of annual opioid deaths shows some agreement. However, the models underestimate the rate of increase observed between 1995 and 1999 and do not entirely capture the rapid decrease in overdose deaths from 2000 onwards. The linkage data showed a peak of overdose deaths at 430 in 1999 compared to 320 estimated by the models. Comparison of observed liver deaths with the modelled numbers showed poor agreement. A good agreement would require an increase in liver deaths from the assumed 2 to 5% per annum following cirrhosis in the models. Mathematical models suggest that HCV incidence decreased from a peak of 14,000 infections in 1999 to 9700 infections in 2005, largely attributable to a reduction in injecting drug use. The poor agreement between projected and linked liver deaths could reflect differing coding of causes of deaths, underestimates of the numbers of people with cirrhosis following HCV, or underestimates of rates of liver death following cirrhosis. The reasonably good agreement between most of the modelled estimates with observed linkage data provides some support for the assumptions used in the models.

Get full access to this article

View all access options for this article.

References

HCVPWG (Hepatitis C Virus Projections Working Group) , 1998. Estimates and projections of the hepatitis C virus epidemic in Australia. NCHECR, UNSW, Sydney , NSW.

HCVPWG (Hepatitis C Virus Projections Working Group) , 2002. Estimates and projections of the hepatitis C virus epidemic in Australia. NCHECR, UNSW, Sydney , NSW.

Nchecr , 2005. Australian NSP Survey National Data Report 2000-2004. NCHECR, UNSW, Sydney, NSW. (available at www.med.unsw.edu.au/nchecr )

Amin J. , Dore GJ , O'Connell D. , Bartlett M. , Kaldor JM , Law MG Cancer incidence in people with hepatitis B or C infection: a large community based linkage study.J Hepatology 2006; 45(2): 197-203.

Amin J. , Law MG , Bartlett M. , Kaldor JM , Dore GJ Causes of death following diagnosis of hepatitis B or C infection: a large community based linkage study. In review, The Lancet 2006; 368(9539): 938-45.

Dore GJ , Law MG , MacDonald M. , Kaldor JMH. Epidemiology of hepatitis C virus infection in Australia. J Clin Virol 2003; 26(2): 171-84.

Crofts N. , Jolley D. , Kaldor J. , van Beek I. , Wodak A. Epidemiology of hepatitis C virus infection among injecting drugs users in Australia. J Epidem Comm Hlth 1997 ; 6: 692-97.

van Beek I. , Dwyer R. , Dore GJ , Luo K. , Kaldor JM High incidence of hepatitis C virus infection among injecting drug users in Sydney in a harm reduction setting. Br Med J 1998; 317: 433-37.

NCHECR (National Centre in HIV Epidemiology and Clinical Research). HIV/AIDS, hepatitis C and sexually transmissible infections in Australia: annual surveillance report, 2001. NCHECR , Sydney, NSW. (available at www.med.unsw.edu.au/nchecr)

10.

Gilmour S. , van Beek I. , Law MG Incidence of hepatitis C in a cohort of injecting drug users, 1993-2000 . In 3rd Australasian Conference on Hepatitis C , Melbourne, March 2002. Delegate book and abstracts, 58.

11.

NCHECR (National Centre in HIV Epidemiology and Clinical Research). HIV/AIDS, viral hepatitis and sexually transmissible infections in Australia Annual Surveillance Report, 2004. National Centre in HIV Epidemiology and Clinical Research, Sydney, NSW; Australian Institute of Health and Welfare, Canberra, ACT. (available at www.med.unsw.edu.au/nchecr )

12.

Topp L. , Day C. , Degenhardt L. Changes in patterns of drug injection concurrent with a sustained reduction in the availability of heroin in Australia. Drug Alcohol Depend 2003; 70: 275-86.

13.

Maher L. , Jalaludin B. , Chant K. , Jayasuriya R. , Sladden T. , Kaldor J. , Sargent P. Incidence and risk factors for hepatitis C seroconversion in injecting drug users in Australia. Addiction 2006; 101: 1499-1508.

14.

Razali K. , Thein HH , Bell J. , Cooper-Stanbury M. , Dolan K. , Dore GJ , George J. et al. Modelling the hepatitis C virus epidemic in Australia. Drug Alcohol Depend 2007; 91(2-3): 228-35.

15.

Law MG on behalf of the Hepatitis C Virus Projections Working Group. Modelling the hepatitis C virus epidemic in Australia. J Hepatology 1999; 14: 1100-07.

16.

Day C. , Topp L. , Rouen D. , Darke S. , Hall W. , Dolan K. Decreased heroin availability in Sydney in early 2001. Addiction 2003; 98: 93-95.

17.

ABCI (Australian Bureau of Criminal Intelligence) , 1998-2004. Australian illicit drug report 1998-1999, 1999-2000, 2000-2001, 2001-2002, 2002-2003, and 2003-2004. ABCI, Canberra.

18.

CDHHS (Commonwealth Department of Health and Human Services) , 1996. National Drug Strategy Household Survey: Survey Report 1995. Canberra, AGPS .

19.

NCHECR (National Centre in HIV Epidemiology and Clinical Research) , 2005. HIV/AIDS, viral hepatitis and sexually transmissible infections in Australia Annual Surveillance Report 2005. NCHECR, Sydney, NSW; AIHW, Canberra, ACT. (available at www.med.unsw.edu.au/nchecr )

20.

AIHW (Australian Institute of Health and Welfare) , 2006. AIHW National Hospital Morbidity Database (available at www.aihw.gov.au/hospitals/datacubes/datacube_pdx.cfm )

21.

Degenhardt L. , Roxburgh A. , Black E. , 2004. 2003 Australian Bureau of Statistics data on accidental opioid induced deaths . NDARC, Sydney. ISSN: 14459833.

22.

Dietze P. , Jolley P. , Cvetkovski S. , Cantwell K. , Jacobs I. , Indig D. Characteristics of non-fatal opioid overdoses attended by ambulance services in Australia. Aust N Z J Pub Hlth 2004; 28: 65-71.

23.

Albano A. , Pianetti A. , Biffi MR , Bruscolini F. , Baffone W. , Albano V. et al. Prevalence of anti-HCV in subjects of various age groups. Eur J Epidemiol 1992; 8: 309-11.

24.

Alberti A. , Noventa F. , Benvegnu L. , Boccato S. , Gatta A. Prevalence of liver disease in a population of asymptomatic persons with hepatitis C virus infection. Ann Intern Med 2002; 137: 961-4.

25.

Thuring EG , Joller-Jemelka HI , Sareth H. , Sokhan U. , Reth C. , Grob P. Prevalence of markers of hepatitis viruses A, B, C and of HIV in healthy individuals and patients of a Cambodian province. Southeast Asian J Trop Med Public Health 1993; 24: 239-49.

26.

Puro V. , Petrosillo N. , Ippolito G. , Aloisi MS , Boumis E. , Rava L. Occupational hepatitis C virus infection in Italian health care workers. Italian Study Group on Occupational Risk of Bloodborne Infections. Am J Public Health 1995; 85: 1272-5.

27.

Kakepoto GN , Bhally HS , Khaliq G. , Kayani N. , Burney IA , Siddiqui T. et al. Epidemiology of blood-borne viruses: a study of healthy blood donors in Southern Pakistan . Southeast Asian J Trop Med Public Health 1996; 27: 703-6.

28.

Xia GL , Liu CB , Cao HL , Bi SL , Zhan MY , Su CA et al. Prevalence of hepatitis B and C virus infections in the general Chinese population: results from a nationwide cross-sectional seroepidemiologic study of hepatitis A, B, C, D, and E virus infections in China, 1992. International Hepatology Communications 1996; 5: 62-73.

29.

Luby SP , Qamruddin K. , Shah AA , Omair A. , Pahsa O. , Khan AJ et al. The relationship between therapeutic injections and high prevalence of hepatitis C infection in Hafizabad, Pakistan. Epidemiol Infect 1997; 119: 349-56.

30.

Frank C. , Mohamed MK , Strickland GT , Lavanchy D. , Arthur RR , Magder LS et al. The role of parenteral antischistosomal therapy in the spread of hepatitis C virus in Egypt. Lancet 2000 ; 355: 887-91.

31.

Khattak MF , Salamat N. , Bhatti FA , Qureshi TZ Seroprevalence of hepatitis B, C and HIV in blood donors in northern Pakistan . J Pak Med Assoc 2002; 52: 398-402.

32.

Micallef J. , Kaldor JM , Dore GJ Spontaneous viral clearance following acute hepatitis C infection: a systematic review of lingitudinal studies. J Vir Hepatitis 2006; 13: 34-41.

33.

Freeman AJ , Dore GJ , Law MG , Thorpe M. , von Overbeck J. , Lloyd AR , Marinos G. , Kaldor JM Estimating progression to cirrhosis in chronic hepatitis C virus infection . J Hepatology 2001; 34: 809-16.

34.

Poynard T. , Ratziu V. , Charlotte F. , Goodman Z. , McHutchison J. , Albrecht J. Rates and risk factors of liver fibrosis progression in patients with chronic hepatitis C. J Hepatology 2001; 34: 730-9.

35.

Fattovich G. , Giustina G. , Degos F. , Tremolada F. , Diodati G. , Almasio P. , Nevens F. , Solinas A. et al. Morbidity and mortality in compensated cirrhosis type C: a retrospective follow-up study of 384 patients. Gastroenterology 1997; 112: 463-72.

36.

ABS (Australian Bureau of Statistics) , 2005. Deaths, Australia 2004. ABS Catalogue No. 3302.0 . AGPS, Canberra, 2002.

37.

AIHW (Australian Institute of Health and Welfare) , 2005. 2004 National Drug Strategy Household Survey: First results. AIHW cat. No. PHE 15. Canberra: AIHW (Drug Statistics Series).

38.

DIMIA (Department of Immigration and Multicultural and Indigenous Affairs) , 2005. Settlement Reports 2005 (available at www.immi.gov.au)

39.

Thorley A. Longitudinal studies of drug dependence. In Edwards G , Busch C (eds). Drug Problems in Britain: A Review of Ten Years. Academic Press, London; 1981.

40.

English D. , Holman CDJ , Milne E. , Winter E. , Hulse GK , Codde JP et al. The Quantification of Drug Caused Morbidity and Mortality in Australia, 1995 edition. Commonwealth Department of Human Services and Health, Canberra.

41.

Ndarc. Opioid Overdose Deaths in Australia, 2003 edition. NDARC, Sydney.

42.

McDonald SA , Donaghy M. , Goldberg DJ , Hutchinson SJ , Robestson C. , Bird SM , Mills PR , Dillon J. , Bloor M. , Hayes P. , Graham L. A population-based record linkage study of mortality in hepatitis C-diagnosed persons with or without HIV coinfection in Scotland. Statistical Methods in Medical Research 2008; DOI: 10.1177/0962280208094890

43.

Hutchinson SJ , Bird SM , Goldberg DJ Modeling the current and future disease burden of hepatitis C among injection drug users in Scotland . J Hepatology 2005; 42: 711-23.

44.

Darke S. , Topp L. , Kaye S. New South Wales Drug Trends 2000: Findings from the Illicit Drug Reporting System (IDRS) Sydney, 2001: NDARC, UNSW.

45.

Darke S. , Topp L. , Kaye S. , Hall W. Heroin use in New South Wales, Australia, 1996-2000: 5-year monitoring of trends in price, purity, availability and use from the Illicit Drug Reporting System (IDRS). Addiction 2002; 97: 179-86.

46.

Rouen D. , Dolan K. , Day C. , Topp L. , Darke S. , Hall W. Changes in heroin availability in Sydney, Australia in Early 2001. NDARC Technical Report No. 119, 2001, UNSW, Sydney.

47.

Stafford J. , Degenhardt L. , Black E. , Bruno R. , Buckingham K. , Fetherston J. , Jenkinson R. , Kinner S. , Moon C. , Weekley J. Australian Drug Trends 2004: Findings from the Illicit Drug Reporting System (IDRS). NDARC Monograph No. 55. Sydney: National Drug and Alcohol Research Centre, University of New South Wales, 2005.