Factors associated with HIV and syphilis co-infection among men who have sex with men in seven Chinese cities.

HIV-syphilis co-infection is often cited as a major reason behind recent resurgence in syphilis prevalence among men who have sex with men in China. Most published literatures explore factors associated with either HIV or syphilis, but not their co-infection. We analysed data from a cross-sectional survey on men who have sex with men in seven Chinese cities. Snowball sampling was used to recruit participants for the survey. Socio-demographic and behavioural predictors for HIV-syphilis mono/co-infection were examined using ordinal logistic regression. Factor scores were used to summarise (1) HIV-related knowledge and (2) access to HIV preventive services. Prevalence of HIV, syphilis, and their co-infection, among 2936 self-identified men who have sex with men, were 7.7%, 14.3%, and 2.6%, respectively. In the adjusted analysis, the significant positive correlates of poorer diagnoses (co-infection vs mono- and no infection or co- and mono-infection vs no infection) were: 30 to 39 years and ≥40 years age, education up to senior high school, unprotected anal intercourse, recent sexually transmitted infection symptoms, incorrect knowledge about routes of transmission, and access to preventive or counselling/testing services for HIV. For effective control of this dual epidemic, integrated HIV and syphilis surveillance and targeted intervention strategies for Chinese men who have sex with men are needed urgently.