The substantial decline in new HIV cases among injection drug users (IDUs) in Baltimore has not been matched by reductions in the number of new hepatitis C cases, according to a study published in the March issue of The Journal of Infection Diseases.

Researchers at the Johns Hopkins School of Public Health in Baltimore studied a number of IDUs at intervals over a twenty-year period. The authors demonstrated that while new cases of HIV and hepatitis C virus (HCV) declined over the study period, the incidence of HIV declined to zero (5.5 per 100 person-years [PY] in 1988 to 1989 compared with 0 in 1998 and 2003 to 2005), while new cases of HCV were still being reported (22 per 100 PY in in 1988 to 1989 compared with 7.8 per PY in 2005 to 2008). The reduction in HCV infections was concentrated among younger IDUs who had only recently started injecting drugs.

An accompanying editorial by Jason Grebely, PhD, and Gregory Dore, PhD, of the University of New South Wales in Australia attributes this difference to the greater prevalence of hepatitis C and to its greater transmissibility-hep C being passed along at a rate 10 times greater than HIV. Sharing needles even once can be enough to transmit hep C, making it a much greater threat to those who make only intermittent use of sterile needles and needle exchange programs. The editorial authors add that harm reduction measures such as needle exchange and opioid substitution treatment don’t get enough support and aren’t sufficiently accessible to drug users.

“Although the HCV prevention window may have a narrow opening,” Grebely and Dore write, “improvements in HCV prevention are feasible. Continued surveillance to monitor trends in drug use, HCV incidence, and risk behaviors is required. The development and implementation of national harm-reduction strategies including broader coverage, enhanced early access, and intensification and combination of interventions are probably all needed. However, randomized controlled trials evaluating HCV interventions, including combined strategies, are required. Furthermore, peer-based education, support, and community participation will be essential for the successful delivery and uptake of intervention strategies.”