Increasing Syphilis Prevalence Among MSM Across India Despite Improvements in the HIV Care Continuum

Introduction: Syphilis rates have increased in many regions, especially in men who have sex with men (MSM). Yet data are sparse from low- and middle-income countries. We characterized changes in syphilis prevalence across serial respondent-driven sampling (RDS) surveys in 10 Indian cities between 2012 and 2024. Methods: We used RDS of MSM in 2012-2013 (10 cities), 2016-2017 (same 10 cities), and 2023-2024 (3 of 10 cities). Participants were ≥18 years, male, and reported sex with a man in the prior 12 months. Participants completed a survey, had a rapid HIV antibody test, with reflex HIV RNA and rapid plasma regain (RPR) confirmed by Treponema pallidum hemagglutination (TPHA) on stored specimens. We assessed syphilis (RPR and TPHA positive) correlates for the 2016-2017 time period using multilevel Poisson regression models, estimating prevalence ratios (PR). Results: Of 9991, 9993, and 2249 participants, median ages were 25, 29, and 28 years, respectively. Almost 50% reported recent condomless anal sex across all rounds. Syphilis prevalence was 2.9%, 7.4%, 15.6% respectively. Less than 10% of participants with positive serology reported a prior diagnosis of syphilis. During the same period, HIV prevalence and viral load suppression doubled. In multivariable analysis, living with HIV (vs. not), ≥2 recent male sexual partners, self-reported history of syphilis, and recent anogenital ulceration was associated with syphilis. Discussion: Syphilis prevalence dramatically increased among MSM over a decade. Concurrently, HIV viremia substantially declined. These data suggest barriers to syphilis testing in urban Indian MSM. Innovations including dual rapid HIV/syphilis antibody tests may increase detection rates.