Hepatitis C virus phylogenetic clustering is associated with the social-injecting network in a cohort of people who inject drugs

Rachel Sacks-Davis, G Daraganova, Campbell K Aitken, Peter Higgs, Lilly Tracy, Scott Bowden, Rebecca Anne Jenkinson, David Rolls, P Pattison, Garry Robins, Jason Grebely, Alyssa Barry, Margaret Elena Hellard

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It is hypothesized that social networks facilitate transmission of the hepatitis C virus (HCV). We tested for association between HCV phylogeny and reported injecting relationships using longitudinal data from a social network design study. People who inject drugs were recruited from street drug markets in Melbourne, Australia. Interviews and blood tests took place three monthly (during 2005-2008), with participants asked to nominate up to five injecting partners at each interview. The HCV core region of individual isolates was then sequenced and phylogenetic trees were constructed. Genetic clusters were identified using bootstrapping (cut-off: 70 ). An adjusted Jaccard similarity coefficient was used to measure the association between the reported injecting relationships and relationships defined by clustering in the phylogenetic analysis (statistical significance assessed using the quadratic assignment procedure). 402 participants consented to participate; 244 HCV infections were observed in 238 individuals. 26 genetic clusters were identified, with 2-7 infections per cluster. Newly acquired infection (AOR = 2.03, 95 CI: 1.04-3.96, p = 0.037, and HCV genotype 3 (vs. genotype 1, AOR = 2.72, 95 CI: 1.48-4.99) were independent predictors of being in a cluster. 54 of participants whose infections were part of a cluster in the phylogenetic analysis reported injecting with at least one other participant in that cluster during the study. Overall, 16 of participants who were infected at study entry and 40 of participants with newly acquired infections had molecular evidence of related infections with at least one injecting partner. Likely transmission clusters identified in phylogenetic analysis correlated with reported injecting relationships (adjusted Jaccard coefficient: 0.300; p
Original languageEnglish
Article numbere47335
Number of pages15
JournalPLoS ONE
Issue number10
Publication statusPublished - 2012

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