Stable Incidence of HIV Diagnoses Among Danish MSM Despite Increased Engagement in Unsafe Sex

Background: Since introduction of highly active antiretroviral therapy (HAART), the prevalence of Danish HIV-positive men who have sex with men (MSM) has increased substantially. In contrast, the incidence of MSM diagnosed with HIV has not increased, and this paradox has been the focus of intensive debate. Methods: Study period was 1995-2010. Data were obtained from 2 Danish nation-wide registries of HIV and syphilis, and 5 consecutive surveys on sexual behavior in Danish MSM. We calculated incidences of HIV and syphilis in MSM, prevalence of HIV-positive MSM with detectable viral load (>400 HIV RNA copies/mL), and changes in frequency of unprotected anal intercourse. We introduce The Cohort Community Reproductive Rate (CCRR) to describe the number of newly diagnosed MSM per HIV-positive MSM per year and used Poisson regression to model CCRR. Results: From 1995 to 2010, the prevalence of Danish MSM diagnosed with HIV increased from 1035 to 1813 (75%), whereas the number of HIV-positive MSM with detectable viral load (>400 HIV RNA copies/mL) decreased by 75% from 1035 to 262. The incidence of syphilis and unprotected anal intercourse rose dramatically in the same period, whereas CCRR decreased from 0.099 (95% confidence interval: 0.092 to 0.108) to 0.071 (95% confidence interval: 0.065 to 0.079). Conclusions: Our results strongly indicate that HAART has decreased the risk of transmission of HIV despite increased practice of unsafe sex and thereby substantiate that HAART should be offered to MSM to reduce risk of transmission of the disease.