Why study hepatitis C in people who inject drugs?

Globally, it is estimated that 170 million people are infected with hepatitis C and the burden of disease associated with hepatitis C is considerable. Approximately 75 percent of new hepatitis C infections progress to chronicity and of those, 15-20 percent develop liver cirrhosis.

In developed countries, the main group at risk of hepatitis C infection are people who inject drugs, with the majority of new infections attributed to injecting drug use (Australia: 90 percent, UK: >90 percent, USA: 54 percent). Globally, the prevalence of hepatitis C infection among people who inject drugs is estimated to be extremely high, much higher than the prevalence of HIV, with approximately 10 million people who inject drugs estimated to be infected with hepatitis C currently or to have been infected with hepatitis C in the past. There is currently no vaccine for hepatitis C.

Why social networks?

If we were to rely on traditional research methods, we would have to make an assumption that the probability of one study participant acquiring hepatitis C is independent of the probability of other study participants' hepatitis C infections. However, the population of people who inject drugs in Melbourne is linked, and hepatitis C is transmitted directly between individuals. If a study participant engages in risky behaviour with another study participant, then their risk of infection will be dependent on the infection status of that participant. Rather than ignore this, we use social network methods to explicitly account for these dependencies.

Study aims

The Networks 2 project is a collaborative project that brings together qualitative and quantitative epidemiologists, social network modellers, virologists and immunologists in order to study the transmission and natural history of the hepatitis C virus in a social network of young people who inject drugs. The aim is to identify behavioural, social, genetic and other biological factors associated with hepatitis C transmission and progression to chronic hepatitis C.

Methods

Project participants were recruited from street illicit drug markets in Melbourne in 2005-2006 and followed over time. At approximately three month intervals, we conduct interviews with participants and collect blood samples. The interviews are designed to collect information about participants' risk behaviour and social connects with other people who inject drugs. The blood samples are used to test for hepatitis C and other blood-borne viruses (hepatitis B and HIV), as well as genetic and immunological markers. In combination with traditional statistical methods, social network and other mathematical models are used to analyse the data at a population level. Qualitative interviews are used to explore social and behavioural issues in more detail.

Publications

2011

• Antigen-driven patterns of TCR bias are shared across diverse outcomes of human hepatitis C virus infection.
  Miles JJ, Thammanichanond D, Moneer S, Nivarthi UK, Kjer-Nielsen L, Tracy SL, Aitken CK, Brennan RM, Zeng W, Marquart L, Jackson D, Burrows SR, Bowden DS, Torresi J, Hellard M, Rossjohn J, McCluskey J, Bharadwaj M
  J Immunol. 2011 Jan; 186(2):901-912

2009

• TCD8 response in diverse outcomes of recurrent exposure to hepatitis C virus.
  Bharadwaj M, Thammanichanond D, Aitken CK, Moneer S, Drummer HE, Tracy S, Holdsworth R, Bowden S, Jackson D, Hellard M, Torresi J, McCluskey J
  Immunol Cell Biol. 2009 Aug; 87(6):464-472
• Heroin-gel capsule cocktails and groin injecting practices among ethnic Vietnamese in Melbourne, Australia.
  Higgs P, Dwyer R, Duong D, Thach ML, Hellard M, Power R, Maher L
  Int J Drug Policy. 2009 Jul; 20(4):340-346
• Markers and risk factors for HCV, HBV and HIV in a network of injecting drug users in Melbourne, Australia.
  Miller ER, Hellard ME, Bowden S, Bharadwaj M, Aitken CK
  J Infect. 2009 May; 58(5):375-382

2008

• High incidence of hepatitis C virus reinfection in a cohort of injecting drug users.
  Aitken CK, Lewis J, Tracy SL, Spelman T, Bowden DS, Bharadwaj M, Drummer H, Hetlard M
  Hepatology. 2008 Dec; 48(6):1746-1752
• Gender, culture and harm: an exploratory study of female heroin users of Vietnamese ethnicity.
  Higgs P, Owada K, Hellard M, Power R, Maher L
  Cult Health Sex. 2008 Oct; 10(7):681-696
• Fiber-modified recombinant adenoviral constructs encoding hepatitis C virus proteins induce potent HCV-specific T cell response.
  Thammanichanond D, Moneer S, Yotnda P, Aitken C, Earnest-Silveira L, Jackson D, Hellard M, McCluskey J, Torresi J, Bharadwaj M
  Clin Immunol. 2008 Sep; 128(3):329-339
• Consecutive infections and clearances of different hepatitis C virus genotypes in an injecting drug user.
  Aitken CK, Tracy SL, Revill P, Bharadwaj M, Bowden DS, Winter RJ, Hellard ME
  J Clin Virol. 2008 Apr; 41(4):293-296
• Integrating enhanced hepatitis C testing and counselling in research.
  Winter R, Nguyen O, Higgs P, Armstrong S, Duong D, Thach ML, Aitken C, Hellard M
  Int J Drug Policy. 2008 Feb; 19(1):66-70

2004

• Molecular epidemiology of hepatitis C virus in a social network of injection drug users.
  Aitken CK, McCaw RF, Bowden DS, Tracy SL, Kelsall JG, Higgs PG, Kerger MJ, Nguyen H, Crofts JN
  J Infect Dis. 2004 Nov; 190(9):1586-1595