Worldwide, over 10 million people who inject drugs (PWID) are chronically infected with hepatitis C (HCV). Few published studies examine incidence patterns, temporal trends, and disease etiology. HCV-negative PWID were selected from pooled epidemiologic data from population-based cohort studies from cites in the US (Boston, Baltimore, and San Francisco), Canada (Montreal), the Netherlands (Amsterdam), and Australia (Sydney and Melbourne). The authors of this study calculated overall and within-city HCV incidence trends, HCV rates 1985–2011, and temporal trends in exposure behaviors. Poisson regression models estimated trends in HCV incidence over calendar-time. Survival models identified risk factors for HCV incidence across cities and estimated independent effects of city and calendar period on HCV infection risk.
- 1391 HCV-negative PWID were followed prospectively for 1644.5 person-years of observation (PYO); 371 incident HCV infections resulted in an overall incidence of 22.6 per 100 PYO.
- Incidence was highest in Baltimore (32.6/100 PYO), San Francisco (24.7/100 PYO), and Montreal (23.5/100 PYO); lowest in Melbourne and Amsterdam (7.5/100 PYO and 13.1/100 PYO, respectively); and moderate in Sydney (21.4/100 PYO).
- Higher rates of syringe and equipment sharing and lower prevalence of opioid agonist therapy were associated with HCV incidence in cities with the highest incidence. In the multivariable model, risk for infection dropped by 18% for every 3-year increase in calendar-time (adjusted hazard ratio, 0.8).
Comments: The results of this study of temporal trends in HCV incidence in large, urban areas are consistent with prior reports that harm reduction strategies and access to opioid agonist treatment (in areas where opioids are the primary injected drug) reduce HCV infection among PWID.
Jeanette M. Tetrault, MD
Reference: Morris MD, Shiboski S, Bruneau J, et al. Geographic differences in temporal incidence trends of hepatitis C virus infection among people who inject drugs: the InC3 Collaboration. Clin Infect Dis. 2017;64:860–869.