The HIV and STI syndemic following mass scale-up of combination HIV interventions in Uganda: a population-based cross-sectional study

Background: Combination HIV interventions (CHIs) have led to significant declines in HIV incidence in sub-Saharan Africa; however, population-level data on non-HIV sexually transmitted infection (STI) burden in the context of CHIs are rare. We aimed to assess STI burden in Uganda following mass scale-up of CHIs, including universal HIV treatment. Methods: The Sexually Transmitted Infection Prevalence Study (STIPS) was a cross-sectional study nested within the Rakai Community Cohort Study (RCCS), a population-based cohort among inland agrarian and Lake Victoria fishing populations in southern Uganda. STIPS enrolled consenting participants, 18-49 years, between May and October 2019 and measured prevalence of Chlamydia trachomatis (chlamydia), Neisseria gonorrhoeae (gonorrhea), Trichomonas vaginalis (trichomonas), syphilis, and herpes simplex virus type 2 (HSV-2). Findings: STIPS enrolled 1,825 participants, including 965 women (53%), of whom 9% (n=107) were pregnant. Overall, there was 9.8% prevalence of chlamydia (95%CI:8.5-11%), 6.7% gonorrhea (95%CI:5.7-8.0%), and 11% trichomonas (95%CI:9.5-12%). In the fishing population, syphilis reactivity was 24% (95%CI:22-27%), with 9.4% (95%CI:7.7-11%) having high titer (RPR [≥]1:8) infection, including 17% (95%CI:12-24%) of HIV-positive men. Prevalence of [≥]1 curable STI (chlamydia, gonorrhea, trichomonas, or high titer syphilis) was 44% higher among HIV-positive persons (adjusted prevalence risk ratio [adjPRR]=1.44,95%CI:1.22-1.71), with no differences by HIV treatment status. HIV-positive pregnant women were more likely than HIV-negative pregnant women to have a curable STI (adjPRR=1.87, 95%CI: 1.08-3.23). Interpretation: STI burden remains extremely high in Uganda, particularly among HIV-positive persons. There is an urgent need to integrate STI diagnostic testing and treatment with HIV services in African settings.