Background Men who have sex with men (MSM) are a key target population for HIV prevention and control in Kenya. Although male sex workers remain the focus of research in Nairobi, HIV/STI prevalence has not been assessed among the wider MSM population since 2010. This study set out to reassess prevalence and associations of HIV and other STIs.

Methods Respondent-driven sampling recruited 618 MSM. Eligibility criteria were age 18+, male (birth or currently), Nairobi residence and consensual oral or anal intercourse with a man in the last year. Consenting participants completed an online survey including current experience of STI symptoms. Participants tested for HIV [Determine, First Response [2^nd gen] and GeneXpert HIV-Qual [4^th gen]], syphilis [RPR/TPHA], hepatitis B and C [HBsAg and HCV ELISA], urine and rectal chlamydia and gonorrhea [GeneXpert CTNG]. Associations with prevalent HIV were assessed using multivariate logistic regression.

Results HIV prevalence was 26.4% [22.6–30.6] including 0.5% [0.2–1.5] detected solely on 4th gen testing. Prevalent HIV was independently associated with age, lower education, Kenyan birth, transgender identity and exclusive sex with men in the past 3 months but dependently associated with STI symptoms. Prevalence of syphilis was 0.8% [0.3–1.9]; hepatitis B 4.4% [3.4–6.9]; hepatitis C 0.5% [0.2–1.5]. Current symptoms consistent with urethritis were reported by 6.4% [4.5–9.0] of participants. Prevalence of urethral GC and CT were 4.4% [2.9–6.7] and 7.3% [5.2–10.3] respectively. Symptoms consistent with proctitis were reported by 8.6% [6.3–11.6] of participants. The prevalence of rectal GC and CT were 13.3% [10.4–16.8] and 8.7% [6.7–11.2] respectively. Overall, only 17.7% [9.2–31.2] of participants with urethral CT/NG and 17.8% [10.7–28.0] rectal CT/NG were symptomatic.

Conclusion The burden of HIV among gay, bisexual and other MSM (GBMSM) remains considerably higher than other men in Nairobi, whilst the prevalence of syphilis and hepatitis C are relatively low. Chlamydia and gonorrhoea infections, particularly rectal, are common and frequently asymptomatic. Capacity of GBMSM-friendly and community-based providers to offer CT/NG screening should be prioritised.