title: Phylogenetic clustering of hepatitis C virus among people who inject drugs in Vancouver, Canada.
abstract: Little is known about factors associated with hepatitis C virus (HCV) transmission among people who inject drugs (PWID). Phylogenetic clustering and associated factors were evaluated among PWID in Vancouver, Canada. Data were derived from the Vancouver Injection Drug Users Study. Participants who were HCV antibody-positive at enrolment and those with HCV antibody seroconversion during follow-up (1996 to 2012) were tested for HCV RNA and sequenced (Core-E2 region). Phylogenetic trees were inferred using maximum likelihood analysis and clusters were identified using ClusterPicker (90% bootstrap threshold, 0.05 genetic distance threshold). Factors associated with clustering were assessed using logistic regression. Among 655 eligible participants, HCV genotype prevalence was: G1a: 48% (n=313), G1b: 6% (n=41), G2a: 3% (n=20), G2b: 7% (n=46), G3a: 33% (n=213), G4a: <1% (n=4), G6a: 1% (n=8), G6e: <1% (n=1), and unclassifiable: 1% (n=9). The mean age was 36 years, 162 (25%) were female, and 164 (25%) were HIV+. Among 501 participants with HCV G1a and G3a, 31% (n=156) were in a pair/cluster. Factors independently associated with phylogenetic clustering included: age <40 (versus age≥40, adjusted odds ratio [AOR]=1.64; 95% confidence interval [CI] 1.03, 2.63), human immunodeficiency virus (HIV) infection (AOR=1.82; 95% CI 1.18, 2.81), HCV seroconversion (AOR=3.05; 95% CI 1.40, 6.66), and recent syringe borrowing (AOR 1.59; 95% CI 1.07, 2.36).
  
  
  CONCLUSIONS
  In this sample of PWID, one-third demonstrated phylogenetic clustering. Factors independently associated with phylogenetic clustering included younger age, recent HCV seroconversion, prevalent HIV infection, and recent syringe borrowing. Strategies to enhance the delivery of prevention and/or treatment strategies to those with HIV and recent HCV seroconversion should be explored, given an increased likelihood of HCV transmission in these subpopulations.
authors.affiliation: Viral Hepatitis Clinical Research Program, The Kirby Institute, UNSW Australia, Sydney NSW, Australia.
authors.forename: B
authors.initials: B
authors.lastname: Jacka
authors.affiliation: Viral Hepatitis Clinical Research Program, The Kirby Institute, UNSW Australia, Sydney NSW, Australia.
authors.forename: T
authors.initials: T
authors.lastname: Applegate
authors.affiliation: BC Centre for Disease Control, Vancouver BC.
authors.forename: M
authors.initials: M
authors.lastname: Krajden
authors.affiliation: BC Centre for Disease Control, Vancouver BC.
authors.forename: A
authors.initials: A
authors.lastname: Olmstead
authors.affiliation: BC Centre for Excellence in HIV/AIDS, St Paul's Hospital, Vancouver BC.
authors.forename: P R
authors.initials: PR
authors.lastname: Harrigan
authors.affiliation: Department of Epidemiology, Brown University, Providence, RI, USA.
authors.forename: Bdl
authors.initials: B
authors.lastname: Marshall
authors.affiliation: BC Centre for Excellence in HIV/AIDS, St Paul's Hospital, Vancouver BC.|School of Public Policy, Simon Fraser University, Vancouver, BC, Canada.
authors.forename: K
authors.initials: K
authors.lastname: DeBeck
authors.affiliation: BC Centre for Excellence in HIV/AIDS, St Paul's Hospital, Vancouver BC.|Department of Family Practice, Faculty of Medicine, University of British Columbia, Vancouver, BC.
authors.forename: M-J
authors.initials: MJ
authors.lastname: Milloy
authors.affiliation: Viral Hepatitis Clinical Research Program, The Kirby Institute, UNSW Australia, Sydney NSW, Australia.
authors.forename: F
authors.initials: F
authors.lastname: Lamoury
authors.affiliation: Department of Zoology, University of Oxford.
authors.forename: O G
authors.initials: OG
authors.lastname: Pybus
authors.affiliation: BC Centre for Excellence in HIV/AIDS, St Paul's Hospital, Vancouver BC.|Division of AIDS, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.
authors.forename: V D
authors.initials: VD
authors.lastname: Lima
authors.affiliation: Department of Zoology, University of Oxford.|Virus Reference Department, Public Health England, London, UK.
authors.forename: G
authors.initials: G
authors.lastname: Magiorkinis
authors.affiliation: BC Centre for Disease Control, Vancouver BC.
authors.forename: V
authors.initials: V
authors.lastname: Montoya
authors.affiliation: BC Centre for Excellence in HIV/AIDS, St Paul's Hospital, Vancouver BC.|Division of AIDS, Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Montaner
authors.affiliation: BC Centre for Excellence in HIV/AIDS, St Paul's Hospital, Vancouver BC.
authors.forename: J
authors.initials: J
authors.lastname: Joy
authors.affiliation: BC Centre for Excellence in HIV/AIDS, St Paul's Hospital, Vancouver BC.
authors.forename: C
authors.initials: C
authors.lastname: Woods
authors.affiliation: BC Centre for Excellence in HIV/AIDS, St Paul's Hospital, Vancouver BC.
authors.forename: S
authors.initials: S
authors.lastname: Dobrer
authors.affiliation: Viral Hepatitis Clinical Research Program, The Kirby Institute, UNSW Australia, Sydney NSW, Australia.
authors.forename: G J
authors.initials: GJ
authors.lastname: Dore
authors.affiliation: BC Centre for Excellence in HIV/AIDS, St Paul's Hospital, Vancouver BC.
authors.forename: A F
authors.initials: AF
authors.lastname: Poon
authors.affiliation: Viral Hepatitis Clinical Research Program, The Kirby Institute, UNSW Australia, Sydney NSW, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Grebely
mesh_terms: D000328:Adult; D001955:British Columbia / Q000453:epidemiology; D016000:Cluster Analysis; D055030:Drug Users; D005260:Female; D016174:Hepacivirus / Q000235:genetics*; D006526:Hepatitis C / Q000453:epidemiology / Q000821:virology*; D006801:Humans; D008297:Male; D010802:Phylogeny; D011446:Prospective Studies