Background Epidemiologic data demonstrates unequal distribution of HIV and STIs among MSM in Peru, with higher risk sub-populations disproportionately affected. Perceptions about partners as source of recent acquired STIs and its correlates could contribute to this epidemic by several mechanisms and serve as basis for future interventions.

Methods 323 MSM and TW from Lima, Peru diagnosed with HIV (45.5%), Syphilis (53.9%), and/or Gonorrhea/Chlamydia (15.2%) within the last month were surveyed to assess partner sexual identity, and perception of most recent sexual partner as source of infection. Prevalence ratios (PR) were calculated using heterosexually-identified partners as the reference category in bivariate and multivariate analysis using partner perceived source of infection as the main outcome.

Results Respondents aged from 18–60 years old (Mean: 30.8, SD: 9.3) and self-identified as Heterosexual (6.0%), Bisexual (17.1%), Homosexual (64.8%), and Transgender (12.1%). Most recent sexual partners identified as Heterosexual (10.3%), Bisexual (41.5%), Homosexual (45.7%), and Transgender (2.5%). Perception of most recent sexual partner as likely/highly likely to be the source of STI transmission was reported by 37.2% (N = 120/323) of respondents. Heterosexually-identified partners were least frequently perceived as the source of STI (24.1% perceived as likely/highly likely source). Transgender partners were most frequently perceived as the source of STI (57.1% likely/highly likely source; PR = 2.4; 95% CI: 1.0–5.9; p = 0.5) followed by Homosexual (45.7% likely/highly likely source; PR = 1.9; 95% CI: 1.0–3.7; p = 0.06) and Bisexual (31.6% likely/highly likely source; PR = 1.3; 95% CI: 0.7–2.6; p = 0.06) partners, demonstrating a borderline statistical significance.

Conclusions Partner sexual identity is associated with perception of infection transmission among MSM in Peru. Overall, trends in perception mirror the actual gradient of HIV burden across sexual identities. Future research should focus on the exact potential causes for this at the individual-level (actual knowledge of the epidemic, discrimination, actual past experiences, etc.) and contexts (norms, beliefs, etc.).