Understanding hepatitis C virus (HCV) transmission among people who inject drugs (PWID) is essential for HCV elimination. We aimed to differentiate reinfections from treatment failures and to identify transmission linkages and associated factors in a cohort of PWID receiving opioid agonist therapy (OAT).
We analyzed baseline and follow-up specimens from 150 PWID from three OAT clinics in the Bronx, NY. NGS data from the hypervariable region 1 of HCV were analyzed using Global Hepatitis Outbreak and Surveillance Technology.
There were three transmission linkages between study participants. Nine participants did not achieve sustained virologic response (SVR): seven had follow-up specimens with similar sequences to baseline and two passed away. Four additional participants achieved SVR but became viremic at later follow-up: two were reinfected with different strains, one had a late treatment failure, and one was transiently viremic 17 months post-treatment. All transmission linkages were from the same OAT clinic and involved spousal or common-law partnerships.
This study highlights the use of next generation sequencing (NGS) as an important tool for identifying viral transmission and to help distinguish relapse and reinfection among PWID. Results reinforce the need for harm reduction interventions among couples and those who report ongoing risk factors following SVR.

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