Incidence of HIV and HCV Among People Who Inject Drugs in Montreal, Canada: Data From the HEPCO Longitudinal Cohort Study, 2011-2025.

Ongoing monitoring of hepatitis C virus (HCV) and HIV incidence among people who inject drugs (PWID) is important for epidemic control and assessing progress towards disease elimination. We estimated trends in HIV and HCV infection incidence in a community-based cohort of PWID in Montreal, Canada. Data from March 2011 to March 2025 were drawn from the HEPCO study of PWID aged ≥ 18 years and living in Montreal. Participants with at least two visits were included in analyses. We used a random point approach to estimate the date of each infection event, imputing each date 1000 times, and Rubin's rules to pool incidence rates and 95% CIs across imputations. A total of 743 participants contributed to HCV analyses, with 152 infection events and incidence of 6.47 per 100 person-years (p-y) (95% CI 6.46-6.49). Incidence peaked in 2013 and declined to 2019 before increasing again post-pandemic. There were 61 primary HCV infection events (incidence: 6.15 per 100 p-y; 95% CI 4.79-7.90) and 91 reinfection events (incidence: 6.71 per 100 p-y; 95% CI 6.69-6.73). A total of 836 participants contributed to HIV analysis, with only eight infections over 3089.89 p-y (incidence: 0.26 per 100 p-y; 95% CI 0.13-0.52). Declining HCV incidence among PWID in Montreal may have reversed, but limited data collection during the years 2020-2021 complicates interpretation. HIV incidence was persistently low. HCV incidence remains above World Health Organization elimination targets, highlighting the need for sustained investment in prevention and linkage to care for PWID.