Background: Outbreaks of syphilis have been described among men who have sex with men (MSM) in many western urban communities in the last few years.

Objectives: To describe the first reported outbreak of syphilis among MSM in Israel within a decade of a constant increase in human immunodeficiency virus (HIV) prevalence.

Methods: All patients diagnosed with syphilis were contacted and asked about their sexual behavior, substance use and previous infections. All were tested for HIV and a phylogenetic analysis was performed. 

Results: A total of 23 (59%) of all 39 male patients diagnosed with primary or secondary syphilis between August 2008 and August 2009 were interviewed. All were MSM and performed anal intercourse, while 13 (55%) reported unprotected anal intercourse. Most participants (21, 91%) practiced unprotected oral intercourse. Nine participants (39%) reported unprotected oral intercourse while using condoms during anal intercourse. Ten participants (43%) reported sexual contacts while traveling abroad in the previous few months. Most participants (96%) were co-infected with HIV, and 15 (68%) were already aware of their HIV infection. Fifteen (66%) reported the use of recreational drugs, alcohol, or both before or during sex. No common source or core transmitters were identified.

Conclusions: This syphilis outbreak included MSM who were co-infected with HIV and were characterized by risky sexual behavior including multiple partners, unprotected anal intercourse and substance use. Future targeted interventions should focus on HIV-infected MSM for secondary prevention.