Changing perspectives : Hepatitis C virus infection in key populations

The studies in this thesis were conducted to improve prevention and disease management of hepatitis C virus (HCV) transmission and infection in two key populations in the Netherlands: people who inject drugs (PWID), and HIV-infected men who have sex with men (MSM). The HCV epidemic among PWID (with an without HIV-coinfection) has been described since the 1990s, but HCV treatment in this population remained limited due to concerns about non-adherence. We showed that active drug users could be adherent to HIV-medication, and that structural social support factors were positively related to adherence. In line with these findings, we demonstrated that, by integrating HCV care in existent harm reduction programmes at the public health service (instead of the hospital), effective HCV treatment was feasible among PWID, despite ongoing drug use and psychiatric co-morbidity. The acute HCV epidemic among HIV-infected MSM became apparent around 2000. We showed that the incidence of primary HCV infection in this population stabilized after an initial increase. We found a high incidence of HCV re-infection, implying that risk behaviour continued after primary infection and treatment. Furthermore, optimal HCV treatment duration was studied. In a case-control study we identified risk factors for HCV transmission related to sexual behaviour. To optimize prevention strategies, we studied awareness of and knowledge on HCV infection among MSM. Lastly, motives for and barriers to implementing HCV risk reduction strategies were explored in a qualitative study. The results indicate that novel ways of improving self-efficacy in implementing HCV risk reduction among MSM are needed.