Cumulative incidence of hepatitis C seroconversion in a cohort of seronegative injecting drug users

Aim. To measure the cumulative incidence of hepatitis C virus seroconversio n over a two year period in a group of seronegative injecting drug users. Methods. The study involved follow-up, in 1996, of a cohort (n=85) of injec ting drug users identified as hepatitis C virus seronegative in 1994. Parti cipants were interviewed about risk factors for hepatitis C. A blood sample was also taken for anti-hepatitis C virus antibody and hepatitis C virus R NA testing. Results. Forty-four participants were interviewed and 39 gave blood for tes ting. Most (80%) were aged 29 years or under and two thirds (n=26) were mal e. Around half reported borrowing (49%) or lending (57%) needles and syring es since 1994 and both of these behaviours were associated with seroconvers ion. The majority (88%) also reported sharing other injecting equipment. Ni ne were anti-hepatitis C virus positive giving a seroconversion rate over t wo years of 23 % (13 per 100 person years). Four out of the nine seropositi ve specimens tested were also hepatitis C virus RNA positive. Conclusions, This study demonstrates a high rate of recent hepatitis C viru s seroconversion amongst a group of New Zealand injecting drug users. Trans mission of hepatitis C virus appears to be unabated by current control meas ures. These findings confirm the need to develop more effective policy and practices to prevent further spt ead, not just of hepatitis C, but of other blood-borne viruses in injecting drug user populations.