Background: Men who have sex with men (MSM) are at high risk of acquiring HIV infection following diagnosis with other sexually transmitted infections (STIs). Identifying the types of STIs associated with the greatest risk of subsequent HIV infection could help target HIV prevention interventions.
Methods: Using matched HIV and STI surveillance data from Washington State from 1/1/2007-6/30/2013, we calculated the incidence of new HIV diagnoses following different STI diagnoses among MSM. Men entered observation at the time of their first STI diagnosis during the study period and exited at the date of HIV diagnosis or 6/30/2013. Cox proportional hazards regression was used to compare rates adjusted for calendar time.
Results: From 1/1/2007-6/30/2013, 6577 HIV-negative MSM were diagnosed with 10,080 bacterial STIs and followed for 17,419 person-years. 314 (4.8%) men were subsequently diagnosed with HIV infection for an overall incidence of 1.6 per 100 person-years (95%CI=1.4-1.8). The estimated incidence of HIV diagnoses among all MSM in the state was 0.4 per 100 person-years. MSM were at the greatest risk of acquiring HIV after being diagnosed with rectal gonorrhea (HIV incidence = 4.1 per 100 person-years), followed by early syphilis (2.8), urethral gonorrhea (1.6), rectal chlamydial infection (1.6), pharyngeal gonorrhea (1.1), late syphilis (1.0), and urethral chlamydial infection (0.6) [p<0.0001 overall]. From 7/1/2011-6/30/2013, 739 MSM were diagnosed with HIV infection in Washington State, of whom 116 (16%) had a history of bacterial STI in the 2 years prior to HIV diagnosis, including 49 (6.6%) with a history of early syphilis or rectal gonorrhea.
Conclusions: MSM diagnosed with rectal gonorrhea and early syphilis were at the greatest risk of acquiring HIV infection post-STI diagnosis. Using STI partner services to target HIV prevention interventions such as PrEP to HIV-negative MSM diagnosed with these infections has potential to reach an extremely high risk population.