title: Modelling the prevalence of HCV amongst people who inject drugs: an investigation into the risks associated with injecting paraphernalia sharing.
abstract: BACKGROUND
  In order to prevent the spread of the hepatitis C virus (HCV) amongst people who inject drugs (PWID), it is imperative that any injecting risk behaviour which may contribute to the transmission of disease has its role quantified. To inform public health organisations, mathematical modelling techniques were used to explore the risk of HCV infection through the sharing of injecting paraphernalia (including filters, cookers and water).
  
  
  METHODS
  A mathematical model was developed for the spread of HCV based on the injecting behaviour of PWID in Scotland, with transmission occurring through the sharing of needles/syringes and other injecting paraphernalia. Numerical simulations were used to estimate the transmission probability for HCV through the sharing of injecting paraphernalia such that the modelled endemic HCV prevalence fitted with that observed amongst PWID in Scotland.
  
  
  RESULTS
  The transmission probability of HCV through injecting paraphernalia was modelled to be over 8 times lower than that through needles/syringes (approximately 0.19-0.30% and 2.5%, respectively), assuming transmission occurs through a combination of at least filters and cookers. In the context of reported needle/syringe and paraphernalia sharing rates in Scotland, it is estimated that 38% and 62% of HCV infections are contributed by these practices, respectively. If needle/syringe sharing rates were to be twice those reported, the contributions would be 70% and 30%, respectively.
  
  
  CONCLUSIONS
  Given that the sharing of injecting paraphernalia among PWID is common, HCV transmission through this route could be contributing to the growing healthcare burden associated with this chronic disease. Every effort should therefore be made to establish (a) the contribution that paraphernalia sharing is making to the spread of HCV, and (b) the effectiveness of services providing sterile paraphernalia in preventing infection.
authors.affiliation: Department of Mathematics and Statistics, University of Strathclyde, Livingstone Tower, 26 Richmond Street, Glasgow G1 1XH, UK. Electronic address: stephen.corson@strath.ac.uk.
authors.forename: Stephen
authors.initials: S
authors.lastname: Corson
authors.forename: David
authors.initials: D
authors.lastname: Greenhalgh
authors.forename: Avril
authors.initials: A
authors.lastname: Taylor
authors.forename: Norah
authors.initials: N
authors.lastname: Palmateer
authors.forename: David
authors.initials: D
authors.lastname: Goldberg
authors.forename: Sharon
authors.initials: S
authors.lastname: Hutchinson
mesh_terms: D003198:Computer Simulation; D006526:Hepatitis C / Q000453:epidemiology / Q000523:psychology* / Q000635:transmission*; D006801:Humans; D015233:Models, Statistical; D016485:Needle Sharing / Q000009:adverse effects* / Q000523:psychology / Q000706:statistics & numerical data; D015995:Prevalence; D012309:Risk-Taking; D012606:Scotland / Q000453:epidemiology; D015819:Substance Abuse, Intravenous / Q000523:psychology*
keywords: HCV; Hepatitis C; Injecting paraphernalia; Mathematical modelling; Needle and syringe sharing; PWID