Incidence of HIV and sexually transmitted diseases (STD) in a cohort of HIV-negative men who have sex with men (MSM).

OBJECTIVE: To determine the prevalence of sexually transmitted diseases (STD) and incidence of and risk factors for STD, including HIV-1, among a cohort of HIV-negative men who have sex with men (MSM).
SETTING: Seattle, Washington, United States. PARTICIPANTS: Prospective cohort of 578 HIV-negative MSM in which risk factors for acquiring a STD over 12 months follow-up were evaluated using a cumulative incidence analysis. MAIN OUTCOME MEASURES: Baseline tests obtained were: herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) Western blots, hepatitis B, and syphilis serologies; anorectal and pharyngeal Neisseria gonorrhoeae (GC) cultures; first-catch urine for leukocyte esterase (LE) and Chlamydia trachomatis (CT) ligase chain reaction (LCR). Men with a positive urine LE had urethral GC cultures obtained. The following outcomes were measured over 12 months follow-up: incident symptomatic bacterial STD (urethritis, proctitis, epididymitis), HSV-1 and HSV-2 seroconversion, and HIV-1 seroconversion. The 31 incident cases of STD (men with bacterial STD) were compared with those 489 men without symptomatic bacterial STD or seroconversion to HSV-1, HSV-2 or HIV-1 infection.
RESULTS: Bacterial STD were found in nine participants at enrollment; there were two cases of nonchlamydial urethritis, two cases of nonchlamydial epididymitis, and five cases of asymptomatic GC infection. At enrollment, HSV-2 antibodies were detected in 149 (26.0%) of 572 men and prior hepatitis B infection in 145 (34.8%) of 417 unvaccinated men. During the 1-year of follow-up, 31 men (5.7/100 person-years) had 34 episodes of a symptomatic bacterial STD syndrome (urethritis, epididymitis or proctitis). Urethritis was the most common STD syndrome, detected in 29 men, of whom 10 had GC and 19 had nongonococcal urethritis. In the 1-year of follow-up, five participants seroconverted to HIV-1 (1.3/100 person-years), four to HSV-2 (1.0/100 person-years), and seven to HSV-1 (4.3/100 person-years). Unprotected insertive anal sex [odds ratio (OR) 2.6; 95% confidence interval (CI) 1.2-5.6]; and nitrite inhalant ('poppers') use (OR, 2.3; 95% CI, 1.0-5.0) were independently associated with incident STD.
CONCLUSIONS: STD and HIV infection continue to be acquired even in a city with an overall low bacterial STD prevalence and among educated MSM receiving regular HIV screening and risk-reduction. Urethritis was the most common STD detected, and public health messages aimed at MSM need to emphasize safe insertive as well as receptive sexual practices.