Background
Men who have sex with men (MSM) are at higher risk of syphilis infection compared to heterosexual men. Since 2018, syphilis prevalence has been increasing in high income countries, with limited data from low- and middle-income countries. We previously observed a 3-fold increase in syphilis prevalence between 2012 and 2017 among MSM in India. We aimed to assess further changes in syphilis prevalence and population characteristics between 2017 and 2024.
Methods
Respondent driven sampling (RDS) was used to accrue cisgender MSM in Bhopal, Delhi, and Hyderabad, India, for cross-sectional surveys in 2016-2017 and 2023-2024. Participants were tested for syphilis using the rapid plasma reagin (RPR) test and RPR+ samples were tested using treponema pallidum hemagglutination assay (TPHA). Syphilis infection is defined as both RPR+ and TPHA+. We examined trends of syphilis prevalence, demographics, and sexual risk behaviors by survey cycle and city. To assess whether changes in the 2023-2024 population vs 2016-2017 could explain changes in syphilis prevalence, we used propensity scores (generated from correlates of syphilis infection – age, sexual orientation, HIV prevalence, unprotected anal intercourse (UAI), recent sex work, and number of male/transgender partners) to indirectly standardize the 2023- 2024 population and re-estimate syphilis prevalence. Analyses incorporated RDS-II weights.
Results
3001 MSM and 2249 MSM from the 2016-2017 and 2023-2024 surveys, respectively, were included. Median age was 27 and 28 in the 2016-2017 and 2023-2024 surveys, respectively. Having a high school education or above increased from 45% to 72%. Syphilis prevalence increased nearly 2.5-fold from 7% to 16%, with increases across all sites (Figure). HIV prevalence increased from 15% to 20%, but prevalence of detectable HIV viremia decreased from 37% to 25%, recent UAI increased from 39% to 47%, and recent history of sex work decreased from 12% to 7%. The indirect standardized syphilis prevalence in the 2023-2024 cycle using propensity scores was 14%.
Conclusions
In these 3 Indian cities, we observed substantial recent increases in syphilis prevalence among MSM. Syphilis prevalence remained high after accounting for changes in population characteristics, including risk behaviors such as UAI. Regardless, these data highlight the urgent need for interventions (e.g., DoxyPEP) to address the rising burden of syphilis and potentially other STIs in low- and middle-income countries.