Mechanisms, management and prevention of anorectal sexually transmitted infections.

Anorectal bacterial sexually transmitted infections, predominantly chlamydia, gonorrhoea and syphilis, represent a substantial and evolving global health challenge, with incidence rising despite widespread testing availability. In this Review, we examine the epidemiology and burden of anorectal sexually transmitted infections, explore the pathogenic mechanisms underlying infection and discuss advances in diagnosis, screening and prevention strategies. Anorectal infections are frequently asymptomatic, particularly among men who have sex with men, in which they often exceed the prevalence of urogenital infections. Asymptomatic persistence results from bacterial adaptation to rectal tissues and attenuated local immune responses that fall below symptom thresholds. Molecular diagnostics have transformed detection capabilities, yet substantial challenges persist in distinguishing viable from non-viable microorganisms, expanding point-of-care testing access and balancing screening benefits against antimicrobial stewardship concerns. Treatment approaches continue to evolve in response to emerging resistance patterns, particularly for gonorrhoea. Promising prevention innovations include doxycycline post-exposure prophylaxis, which substantially reduces chlamydia and syphilis incidence and artificial intelligence applications. However, practical implementation in diverse clinical settings remains limited. We highlight important gaps in knowledge and propose research priorities to advance effective control strategies.