Risk factors of syphilis co-infection among HIV-infected men who have sex with men in Tel-Aviv, Israel.

Syphilis incidence in Israel and other industrialized countries has increased in the past decade, mainly among men who have sex with men (MSM) who were co-infected with HIV. This study aimed to assess the demographic characteristics and behavioral risk factors for syphilis infection among HIV-infected MSM in the Tel-Aviv region, Israel. This cross-sectional study compared HIV-infected MSM who were co-infected with syphilis since 2005 with HIV-infected MSM without syphilis, using an anonymous self-administered questionnaire distributed at the AIDS treatment clinic in central Israel in 2016. This study included 75 HIV-infected MSM who were diagnosed with syphilis after their HIV diagnosis and 99 HIV-infected MSM without syphilis. Variables associated with syphilis infection included inadequate adherence to antiretroviral therapy (ART) (OR = 1.8 [1.2-2.4]), frequent unprotected receptive anal intercourse (UAI) with casual sex partners (OR = 2.2 [1.5-8.2]), especially with HIV-infected partner (OR = 3.2 [1.1-7.9]). In conclusion, HIV and syphilis co-infection were associated with frequent UAI with casual sex partners, inadequate adherence to ART and limited partner notification. In order to minimize syphilis transmission among HIV-infected MSM, AIDS clinics should encourage HIV-infected MSM to use condoms, ensure that patients perform periodic syphilis serology testing and improve partner notifications.