Hepatitis C virus transmission in people who inject drugs: swabs may not be the main culprit.

TO THE EDITOR—We read with interest the recent article by Thibault et al [1], which described laboratory analyses of injection equipment collected from people who inject drugs in France. In particular, the detection of hepatitis C virus (HCV) RNA in 80% of pooled samples of alcohol and cotton swabs raises concerns about the possible role of swabs in HCV transmission. While the accompanying editorial notes that " [c]onfirming these results with epide-miologic studies may take time " [2p1820], we present early epidemiological data on this relationship. Between 1999 and 2002, we conducted a longitudinal study of anti-HCV– negative people who inject drugs in 3 sites in New South Wales, Australia [3– 5]. A total of 68 incident cases of HCV infection were observed (30.8 cases/100 person-years; 95% confidence interval [CI], 24.3–39.0). Independent predictors of seroconversion were injection history of <1 year (adjusted hazard ratio [HR], The baseline prevalence of swab sharing (defined as " wiping your injection site with a swab previously used to wipe another person's injection site in the last 6 months ") was 6%. In contrast to receptive syringe sharing (unadjusted swabs was not associated with HCV ser-oconversion (unadjusted HR, 0.68; 95% CI, .21–2.15). As suggested in the accompanying editorial [2], ideally the association between swab sharing and HCV seroconversion should be studied in cohorts with a low prevalence of receptive syringe and container sharing and at least a modest amount of swab sharing. Despite being conducted in a setting of high harm reduction coverage including needle and syringe programs and opioid substitution treatment [6], our cohort had both high prevalence of receptive syringe sharing (27% in the previous 6 months) and container (ie, spoon) sharing (25%), relative to swab sharing (6%) at baseline. While the prevalence of swab sharing was low in our cohort and we were unable to detect a statistically significant relationship between this behavior and incident HCV infection, it would appear prudent to continue to emphasize avoidance of swab reuse in this population. Impact of a reduction in heroin availability on patterns of drug use, risk behaviour and incidence of hepatitis C virus infection in injecting drug Estimating population attributable risk for hepatitis C seroconversion in injecting drug users in Australia: implications for prevention policy and planning.