BACKGROUND: During 2011–2015, Idaho’s syphilis incidence rate increased from 2.65/100,000 persons to 6.16/100,000 persons. Since January 2015, southwestern Idaho has been experiencing a syphilis outbreak, with 3 persons having repeat infections during 2015. We sought to characterize persons with repeat syphilis infection in Idaho.
METHODS: We analyzed sexually transmitted disease (STD) surveillance data maintained by the Idaho Division of Public Health. We defined repeat cases as having ≥2 early syphilis infections (primary, secondary, or early latent stages), and nonrepeat cases as having 1 early syphilis infection reported during 2011–2015. To reduce misclassification, we excluded one person who had early syphilis infection during 2006–2011 from persons with nonrepeat cases. We reviewed demographic, clinical, and epidemiologic information collected during syphilis investigations. We used Median and Fisher's exact tests to describe and compare characteristics of persons with repeat and nonrepeat cases.
RESULTS: During 2011–2015, early syphilis infections were reported in 193 Idaho residents, including 14 (7%) repeat cases. Among persons with repeat cases, 100% were male, 93% were white, 85% [11/13] were non-Hispanic, and 91% [10/11] had male sex partners. Compared with nonrepeat cases, persons with repeat cases more likely had secondary or early latent syphilis (93% [13/14] versus 64% [114/179]; P = 0.037), were HIV-positive (85% [11/13] versus 30% [39/129]; P <0.001), and had a history of STD (82% [9/11] versus 39% [51/132]; P = 0.009). No persons with repeat cases were incarcerated or exchanged sex for drugs or money.
CONCLUSIONS: Repeat syphilis infection in Idaho was associated with HIV infection and history of STD. These characteristics could be used to enhance STD/HIV testing, interview, and partner services to prevent syphilis reinfection.