Risk factors for repeat syphilis in men who have sex with men, San Francisco.

BACKGROUND Syphilis incidence has increased dramatically in the United States since 2000, occurring primarily among men who have sex with men (MSM) and disproportionately affecting those with human immunodeficiency virus (HIV) infection. The continued increases in syphilis rates among MSM signals the need for enhanced prevention methods. We undertook a study to examine the rate of repeat syphilis infection among MSM in San Francisco and to identify risk factors associated with syphilis reinfection that may inform additional prevention strategies. METHODS We developed a retrospective cohort of all cases of primary, secondary, and early latent syphilis among MSM diagnosed in San Francisco in 2001 and 2002. We evaluated data through the end of 2003 to determine all cases of syphilis reinfection, defined as a new infection that occurred within 1 year after prior syphilis infection and treatment. RESULTS We found that 6.7% (42/624) of cases had a repeat syphilis infection within 1 year. HIV infection was associated with an increased risk of repeat infection (OR = 4.7; CI, 1.8-12.0). No differences in age, race, number of period sex partners, illicit substance use, or partner meeting venues were observed between cases with and without repeat infection. CONCLUSIONS Our study revealed that HIV-infected MSM with syphilis represent an at-risk group for repeat syphilis infection. Targeting increased screening and risk reduction interventions to HIV-infected MSM in care could reduce the overall incidence of syphilis among MSM.