Repeat Syphilis Infection in Chicago, 2000-2014 - Need for Alternative Strategies for Disease Control

Background:  In the past 14 years, syphilis in Chicago increased by 90% (497 cases in 2000 to 944 in 2014). Our objective was to describe characteristics of individuals with repeat infection.

Methods:  Early syphilis (ES) included cases of Primary & Secondary and Early Latent stages of disease.  Surveillance data were analyzed using SAS version 9.4. “Repeaters” had two or more episodes of ES syphilis during the study period and “Non-Repeaters” had a single episode of ES syphilis.                                  

Results:  Between 2000-2014, 10,456 ES cases were reported to the Chicago Department of Public Health. Approximately 85% (8,769) of cases were among males of which men who have sex with men (MSM) comprise 64% of the cases. The majority, 80% (8,345) of persons diagnosed with ES were “Non-Repeaters” while 20% (2,111) of persons were “Repeaters”. Overall, there was 1.7% (p<0.001) yearly increase in repeat infections (blacks 1.7%, whites 1.9%, p<0.001). Greater increases in repeat infections were seen among MSM (1.8%, p<0.001) compared to females (0.4%, p<0.001) and heterosexual males (0.8%, p<0.001). “Repeaters" were predominantly males (96.1%), MSM (69.2%), HIV-positive (46%), and with a median age of 37.3 years (Range15–70). Among MSM-Repeaters, yearly increase in repeat infection was significant for Blacks (2.5%) and whites (1.8%). HIV-positive individuals were significantly more likely to have a repeat infection (OR=4.86; 95% CI: 4.17–5.67) than HIV-negative individuals.

Conclusions:  The findings in this report indicate an increasing rate of repeat syphilis infections among all persons with the greatest increase in rate found among Black MSM. The changing epidemiology of ES highlights the need for timely and innovative strategies for syphilis control tailored to reach out population most affected by syphilis.