The Natural History of Rectal Gonococcal and Chlamydial Infections: the ExGen Study.

Background The duration of rectal gonococcal and chlamydial infection remains unknown. This basic epidemiologic parameter is needed to understand transmission dynamics. Methods We conducted a prospective, longitudinal, observational, cohort study of 140 men who have sex with men (MSM) at-risk of gonorrhea and chlamydia acquisition. For 48 weeks, enrolled men collected rectal swabs (Aptima multitest kit) at home and responded to an electronic survey about sexual behavior and health conditions weekly. Swabs remained untested until participants completed the study. We used Kaplan Meier estimates to determine the median duration of infection, censoring infections for treatment, loss-to-follow-up and end-of-study. We used Log-rank test to compare duration of infection by HIV status, history of infection with gonorrhea or chlamydia, and co-infection with the other pathogen. Results 140 enrolled MSM contributed 70.5 person years of follow-up. Eighteen men had 20 incident rectal gonococcal infections, which persisted for 2 - 23 weeks; 30% were censored for treatment. The estimated median duration of rectal gonorrhea was 9 weeks (95% CI: 3-12 weeks). Twenty-four men experienced 32 rectal chlamydial infections, persisting between 2 to 42 weeks; 60% were censored. The estimated duration of rectal chlamydia was 13 weeks (95% CI: 6 weeks - undefined). There were no differences in the duration of rectal gonorrhea or chlamydia by HIV status, history of chlamydia/gonorrhea or co-infection. Conclusions On average, rectal gonorrhea and chlamydial infections last 2-3 months, though some infections some persist for 6-11 months. Further understanding into predictors of persistence are needed.