title: Transmission patterns of HIV and hepatitis C virus among networks of people who inject drugs.
abstract: BACKGROUND
  The risk-related behaviours and practices associated with injection drug use remain a driver of HIV and hepatitis C virus (HCV) transmission throughout the world. Here we evaluated HIV and HCV transmission patterns in the context of social networks of injection drug users (IDU) recruited from a higher incidence region in order to better understand factors that contribute to ongoing transmission among IDU.
  
  
  METHODS
  IDU recruited through a chain-referral method provided biological specimens for analysis. HIV and HCV positive specimens were sequenced and analyzed using phylogenetic methods (Neighbour-joining and bayesian) and transmission patterns of HIV and HCV evaluated in the context of the recruitment networks.
  
  
  RESULTS
  Among the 407 recruited IDU, HCV and HIV prevalence were 60.6% and 10.1%, respectively; 98% of HIV positive individuals were co-infected with HCV. Thirty-six percent of HCV sequences were associated with clusters, compared to 67% of HIV sequences. Four (16.7%) of the 24 HCV clusters contained membership separated by 2 or fewer recruitment cycles, compared to 10 (41.6%) derived from more than one recruitment component. Two (28.6%) of the 7 HIV clusters contained membership separated by 2 or fewer recruitment cycles while 6 (85.7%) were composed of inter component membership.
  
  
  CONCLUSIONS
  Few HIV and HCV transmissions coincided with the recruitment networks, suggesting that they occurred in a different social context or a context not captured by the recruitment network. However, among the complete cohort, a higher degree of HIV clustering indicates many are recent infections originating from within current social networks, whereas a larger proportion of HCV infections may have occurred earlier in injecting history and in the context of a different social environment.
authors.affiliation: National HIV and Retrovirology Laboratories, Public Health Agency of Canada, Ottawa, Ontario, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Pilon
authors.forename: Lynne
authors.initials: L
authors.lastname: Leonard
authors.forename: John
authors.initials: J
authors.lastname: Kim
authors.forename: Dominic
authors.initials: D
authors.lastname: Vallee
authors.forename: Emily
authors.initials: E
authors.lastname: De Rubeis
authors.forename: Ann M
authors.initials: AM
authors.lastname: Jolly
authors.forename: John
authors.initials: J
authors.lastname: Wylie
authors.forename: Linda
authors.initials: L
authors.lastname: Pelude
authors.forename: Paul
authors.initials: P
authors.lastname: Sandstrom
mesh_terms: D016000:Cluster Analysis; D055030:Drug Users; D005260:Female; D060005:Genotyping Techniques; D015658:HIV Infections / Q000097:blood / Q000635:transmission*; D015497:HIV-1 / Q000235:genetics / Q000472:pathogenicity; D016174:Hepacivirus / Q000235:genetics / Q000472:pathogenicity; D006526:Hepatitis C / Q000097:blood / Q000635:transmission*; D006801:Humans; D007267:Injections; D008297:Male; D012309:Risk-Taking; D012698:Serologic Tests; D060756:Social Networking