Objective  To analyze the sentinel acquired immunodeficiency syndrome (AIDS) surveillance data in men who have sex with men (MSM) in the Pearl River Delta area, Guangdong province, from 2016 to 2024, understand the epidemiological trends of human immunodeficiency virus (HIV) infection and syphilis prevalence, as well as AIDS-related knowledge awareness and sexual behaviors in the MSM, and provide evidence for the development of targeted HIV prevention and control strategies.

Methods  The behavioral surveillance data and serological test results were collected from the MSM selected through venue-based sampling, internet recruitment, and respondent-driven sampling. Temporal trends were analyzed by using trend χ² tests.

Results  In the 23 236 MSM surveyed from 2016 to 2024, the HIV infection rate fluctuated between 5.60% and 9.98% (χ²=31.843, P＜0.001), with the highest infection rate in the MSM aged ≥45 years. The prevalence rate of syphilis increased from 4.59% to 5.35% (χ²=14.464, P＜0.001) with a similar increasing trend (2.81% to 5.56%) in the young MSM aged 16−24 years (χ²=17.132, P<0.001). The awareness rate of AIDS ralated knowledge from 88.62% to 95.46% during the study period (χ²=134.721, P<0.001). However, in young MSM aged 16−24 years, there was no statistically significant difference in the trend of the knowledge awareness rate regarding two points: that HIV infection could not be judged by appearance (χ²=2.504, P=0.114) and that other sexually transmitted infections (STIs) would increase the risk for HIV infection (χ²=0.452, P=0.502). Condom use at each sex (both homosex and heterosex) in the past 6 months were improved (both P<0.05), while the condom use at homosexual anal sex in MSM aged 16−24 years showed no significant difference (χ²=3.476, P=0.062).

Conclusion The study revealed persistently high HIV infection and ongoing syphilis transmission in MSM, especially in those aged 16−24 years and ≥45 years. Although the awareness of AIDS related knowledge were improved in all the age group, specific knowledge gaps persist in young MSM aged 16−24 years, regarding HIV/STI co-infection risks and disease manifestations. The high-risk sexual behaviors still existed, especially in young MSM. There is an urgent need to implement full-scale, precision-oriented interventions targeting both young and middle-aged/elderly MSM. Meanwhile, efforts should be made to improve the transformation of HIV prevention and control strategies from traditional health education to a model integrating "behavioral improvement and structural intervention" to reduce high-risk behaviors and establish correct health cognition.