Repeat Syphilis Among Men Who Have Sex With Men in California, 2002–2006: Implications for Syphilis Elimination Efforts

摘要

Objectives. We examined rates of and risk factors for repeat syphilis infection among men who have sex with men (MSM) in California. Methods. We analyzed 2002 to 2006 California syphilis surveillance system data. Results. During the study period, a mean of 5.9% (range: 4.9%–7.1% per year) of MSM had a repeat primary or secondary (PS) syphilis infection within 2 years of an initial infection. There was no significant increase in the annual proportion of MSM with a repeat syphilis infection ( P = .42). In a multivariable model, factors associated with repeat syphilis infection were HIV infection (odds ratio [OR] = 1.65; 95% confidence interval [CI] = 1.14, 2.37), Black race (OR = 1.84; 95% CI = 1.12, 3.04), and 10 or more recent sex partners (OR = 1.99; 95% CI = 1.12, 3.50). Conclusions. Approximately 6% of MSM in California have a repeat PS syphilis infection within 2 years of an initial infection. HIV infection, Black race, and having multiple sex partners are associated with increased odds of repeat infection. Syphilis elimination efforts should include messages about the risk for repeat infection and the importance of follow-up testing. Public health attention to individuals repeatedly infected with syphilis may help reduce local disease burdens. Syphilis incidence rates have risen dramatically in California over the past decade. After reaching a nadir of 687 cases in 2000, the number of early cases of syphilis (primary, secondary, and early latent) in California increased from 1802 (5.1 per 100 000 population) in 2002 to 3836 (10.2 per 100 000 population) in 2008. 1 Between 70% and 80% of syphilis cases in California occur among men who have sex with men (MSM), and in 2008, 57.2% of MSM with primary or secondary (PS) syphilis reported that they were infected with HIV. 1,2 Similar trends in syphilis infections have been reported throughout the United States and Europe. 3–6 Syphilis causes significant morbidity, has long-term sequelae if untreated, and is associated with both HIV transmission and acquisition. 3,7–11 MSM who contract a repeat syphilis infection may disproportionately contribute to transmission of the disease. 12,13 Enhanced, focused public health interventions designed to address the needs of MSM with repeat syphilis may slow syphilis transmission and play an important role in elimination efforts. However, it is not known whether rates of repeat syphilis infection have increased with the rise in syphilis rates or which factors affect risk for repeat infection. Several studies have identified HIV infection as a risk factor for repeat syphilis infection, 14–18 but it is unclear which factors mediate this association. The association may be confounded by common behavioral risk factors such as methamphetamine use and unprotected sexual activity. Previous studies of repeat syphilis infection have included primary, secondary, and early latent syphilis cases (hereafter referred to as early syphilis). 14–19 Including early latent syphilis cases in an analysis of repeat syphilis infection may introduce detection bias, in that HIV-infected MSM are screened frequently for syphilis (often in the setting of routine CD4 and HIV viral load monitoring) and therefore may be more likely than are HIV-uninfected MSM to have an early latent infection detected. 20,21 Identifying risk factors for and delineating trends in repeat syphilis infection are important for the design and implementation of targeted syphilis prevention strategies. We performed a retrospective cohort analysis of syphilis cases during 2002 to 2006 among MSM in California to determine whether the annual proportion of MSM who contracted a repeat syphilis infection within the subsequent 2 years increased and to identify risk factors for repeat infection. To limit the impact of detection bias on the magnitude of the association between HIV and repeat syphilis infection, we limited our primary analysis to symptomatic (i.e., PS) syphilis cases at baseline and during follow-up.