Epidemiology of Treponema pallidum, Chlamydia trachomatis, Neisseria gonorrhoeae and Trichomonas vaginalis among forcibly displaced populations: a global systematic review and meta-analysis.

BACKGROUND

Curable sexually transmitted infections (STIs), including Treponema pallidum (syphilis), Chlamydia trachomatis, Neisseria gonorrhoeae and Trichomonas vaginalis, remain a major global health concern; yet their epidemiology among forcibly displaced populations is poorly understood. Limited access to healthcare, high-risk exposures and structural vulnerabilities may contribute to a heightened burden of STIs in these populations.

METHODS

A systematic review conducted up to 12 July 2024 assessed the prevalence of syphilis, C. trachomatis, N. gonorrhoeae and T. vaginalis infections among refugees, asylum seekers and internally displaced populations globally. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. Pooled mean prevalence of current and/or lifetime infection for each STI was estimated through random-effects meta-analyses. Random-effects meta-regression analysis was feasible for syphilis and investigated sources of heterogeneity, associated factors and temporal trends in prevalence.

RESULTS

The review identified 82 reports contributing 232 prevalence measures based on over 1.1 million test results, with syphilis being the most frequently studied STI. The estimated pooled mean prevalence of current infection was 0.94% (95% CI 0.53% to 1.45%) for syphilis, 0.87% (95% CI 0.33% to 1.61%) for C. trachomatis, 0.14% (95% CI 0.06% to 0.32%) for N. gonorrhoeae and 17.07% (95% CI 0.07% to 51.37%) for T. vaginalis. The prevalence of lifetime syphilis was 2.78% (95% CI 1.54% to 4.31%). Meta-regression analyses explained 64% of the variation in syphilis prevalence. Populations displaced from the African region had a 2.90-fold higher prevalence of syphilis compared with those from the Eastern Mediterranean region (95% CI 1.58 to 5.33), and those hosted in low-income countries had a 5.20-fold higher prevalence than those in high-income countries (95% CI 1.47 to 18.38). Syphilis prevalence declined over time at a relative annual rate of 6%.

CONCLUSION

This review highlights a substantial burden of syphilis among forcibly displaced populations, suggesting active transmission. Evidence for the other curable STIs is more limited, hindering a comprehensive understanding of their epidemiology in humanitarian settings. Systematic screening campaigns and effective STI surveillance are urgently needed, particularly in low-resource settings.