Background: We assessed in drug users the factors associated with prevalence, activity, and genotype of Hepatitis C Virus (HCV) infection, which is an increasing cause of co-morbidity and mortality in persons with HIV infection.

Methods: Standardized interview of current and former drug users and assay of HCV serum antibody, RNA level, and genotype, HIV antibody and viral load, CD4⁺ lymphocyte counts, and hepatitis B markers.

Results: We enrolled 557 drug users; 318 (57%) were men, 82 (14.7%) white, 105 (18.9%) black, and 366 (65.7%) Hispanic; median age was 44 years (range 25–72); 328 (58.9%) were HIV⁺, median HIV load was 1,247 copies/ml (range < 50 – 5 x 10⁵). One hundred fifty-seven (157; 28.2%) reported never having injected drugs. Four hundred eighteen (418; 75%) were anti-HCV⁺, of whom 313 (75%) had detectable HCV RNA (median 5.04 x 10⁵ IU/mL, range 1,020 to 15.7 x 10⁶). On multivariate analysis HCV seropositivity was independently associated with history of drug injection (OR_adj = 22.6, 95% CI, 13.1–39.0), HIV seropositivity (OR_adj = 5.3, 95% CI, 2.8–10.2), and increased age (OR_adj = 1.1 per year, 95% CI, 1.04–1.1), and inversely with drug snorting (OR_adj = 0.02, 95% CI, 0–0.7). Among anti-HCV positive persons, detectable HCV RNA (³ 600 IU/ml) was independently associated with HIV seropositivity (OR_adj = 2.3, 95%CI 1.5-3.7), male gender (OR_adj = 2.2, 95% CI, 1.4–3.5), and history of injection (OR_adj = 1.5, 95% CI, 1.02–2.3), and inversely associated with HBsAg (OR_adj = 0.14, 95% CI, .03–0.6). Among persons with detectable HCV RNA, higher levels were independently associated with higher HIV viral load (p = 0.048), increased age (p = 0.04), and genotypes 2a and 2b (p = 0.003).

Conclusions: Among drug users, drug snorting was inversely associated with risk of HCV infection. Detectable HCV RNA was associated with HIV infection, male gender, and history of injection, and inversely associated with HBsAg. HCV RNA level was associated with HIV viral load, independent of the level of immunosuppression, increased age, and genotypes 2a and 2b. However, a substantial degree of the person-to-person variability in the prevalence and level of detectable HCV RNA remains unexplained.