Risk factors and incidence of sexually transmitted infections in the Swiss HIV Cohort Study.  Open Forum Infectious Diseases
Bosetti and Mugglin et al. assessed the incidence and related risk factors of sexually transmitted infections (STI) among people living with HIV in the Swiss HIV Cohort Study (SHCS).
The authors considered all sexually active cohort participants with follow-up between April 2017 and November 2019. All individuals were screened for syphilis every two years or yearly if they were men who have sex with men (MSM). Testing for chlamydia and gonorrhea was performed at the discretion of cohort physicians and included asymptomatic screening as well as targeted testing of symptomatic individuals. Risk factors for STIs were evaluated using multivariable Poisson regression.
The study included 7’667 sexually active individuals (median age 51 years, 27.2% were women, 46.7% were MSM). During 17’766 person-years (PY) of follow-up, 1’634 STIs were reported (incidence rate 91.9 per 1000 PY), with 41.1% of STIs being asymptomatic. Of those, syphilis was diagnosed in 573 episodes (35.1%), followed by gonorrhea in 497 episodes (30.4%), and 418 (25.6%) episodes were chlamydia infections. The most important risk factors for any STI were male sex (adjusted incidence rate ratio [aIRR] 2.03, 95% CI 1.36–3.02), being MSM (aIRR 3.62, 2.99–4.55), age 18-34 years (aIRR 1.78, 1.51–2.10), having occasional sexual partners (aIRR 6.87, 5.40–8.73) and injecting drug use (aIRR 2.48, 1.91–3.23).
In summary, the present study shows a high incidence of STIs in the SHCS. Together with the high proportion of asymptomatic infections, these findings underline the importance of performing regular screening of sexually active individuals with risk factors for STIs.