High rates of sexually transmissible infections in HIV-positive patients in the Australian HIV Observational Database: a prospective cohort study

Background: In HIV-positive people, sexually transmissible infections (STIs) probably increase the infectiousness of HIV. Methods: In 2010, we established a cohort of individuals (n = 554) from clinics in the Australian HIV Observational Database (AHOD). We calculated retrospective rates for four STIs for 2005-10 and prospective incidence rates for 2010-11. Results: At baseline (2010), patient characteristics were similar to the rest of AHOD. Overall incidence was 12.5 per 100 person-years. Chlamydial infections increased from 3.4 per 100 person-years (95% confidence interval (CI): 1.9-5.7) in 2005 to 6.7 per 100 person-years (95% CI: 4.5-9.5) in 2011, peaking in 2010 (8.1 per 100 person-years; 95% CI: 5.6-11.2). Cases were distributed among rectal (61.9%), urethral (34%) and pharyngeal (6.3%) sites. Gonococcal infections increased, peaking in 2010 (4.7 per 100 person-years; 95% CI: 5.6-11.2; P-trend = 0.0099), distributed among rectal (63.9%), urethral (27.9%) and pharyngeal (14.8%) sites. Syphilis showed several peaks, the largest in 2008 (5.3 per 100 person-years; 95% CI: 3.3-8.0); the overall trend was not significant (P = 0.113). Genital warts declined from 7.5 per 100 person-years (95% CI: 4.8-11.3) in 2005 to 2.4 per 100 person-years (95% CI: 1.1-4.5) in 2011 (P-trend = 0.0016). Conclusions: For chlamydial and gonococcal infections, incidence was higher than previous Australian estimates among HIV-infected men who have sex with men, increasing during 2005-2011. Rectal infections outnumbered infections at other sites. Syphilis incidence remained high but did not increase; that of genital warts was lower and decreased.