Background:
After peaking in 2002, syphilis among men who have sex with men (MSM) declined in Chicago during 2003-2004, only to re-emerge in 2005.

Objective:
To determine if some persons were repeatedly acquiring early syphilis (ES) and potentially acting as a core group of high-frequency transmitters.

Method:
ES cases reported to the Chicago Department of Public Health (CDPH) between 2000-2005 were analyzed for persons who acquired multiple new episodes of ES. Characteristics of persons with repeat ES were compared to those reported only once.

Result:
Between 1/2000 and 9/2005, 3,463 cases of ES were reported involving 3,326 persons; 137 (4.1%) had > one infection. Of the 1,578 ES reports in MSM, 166 (10.5%) were repeat infections. Of 1,489 MSM who acquired ES, 127 (8.5%) acquired it > once, compared to 0.8% females and 0.4% heterosexual men. During the 5 ¾ years of study, 114 persons acquired ES twice; 18 had three episodes, four had four episodes, and one had five episodes; all with ≥ 3 ES episodes were MSM. MSM with multiple ES did not differ from those with one ES episode by age (median age 35 vs 34 years, respectively), or report of anonymous sex partners (58% vs 59%), but were more likely to be HIV infected at initial diagnosis (55% vs 42%) and to be white (65% vs 51%). HIV seroconversion between ES episodes were noted for 9% MSM with repeat ES; median time between episodes was 20 months.

Conclusion:
Many MSM, especially HIV-infected MSM, acquired early syphilis on multiple occasions between 2000 and 2005, and likely represent very high risk “core” transmitters” whose sexual networks maintain a syphilis reservoir in the MSM community.

Implications:
These data highlight the critical need for effective testing, counseling and prevention strategies for these high risk MSM.