Characteristics of HIV and Syphilis Co-Morbidity in Houston, Texas, 1999-2007

Background: CDC estimates that individuals with syphilis are 2 to 5 times more likely to acquire HIV when exposed. Moreover, the presence of syphilis itself is a marker of unsafe sexual practices. Recently the Houston Department of Health and Human Services examined the rates and emerging trends in HIV and syphilis co-morbidity.

Objectives: To describe HIV and syphilis co-morbidity trends in Houston, Texas from 1999 to 2007.

Methods: Surveillance data from the HIV/AIDS Reporting System were matched to data in the Sexually Transmitted Disease Management Information System between 1999 and 2007. Demographic and risk characteristics of individuals with co-infections and those with HIV only were compared and associated odds ratios and 95% confidence intervals calculated using SAS.

Results: Among the 11,567 reported HIV cases, 599 (5%) syphilis cases matched to those captured in the HIV surveillance database. In Houston, the prevalence of HIV and syphilis co-morbidity among persons with HIV increased from 4% to nearly 8% between 1999 and 2007. Ninety-five percent of the co-morbid individuals were male compared with 71% of individuals with HIV only (aOR=2.5, 95% CI =1.6–3.9). Men who have sex with men (MSM) were 5.5 times more likely to experience co-morbidity compared to high risk heterosexuals (aOR=5.5; 95% CI=3.8-8.0). The likelihood of co-morbidity decreased as age increased.

Conclusions: The prevalence of HIV and syphilis co-morbidity among HIV-infected individuals in Houston nearly doubled between 1999 and 2007. Co-morbid individuals were different in demographic and risk factors from individuals with HIV infection only. Co-morbid individuals were more likely to be MSM, younger, and diagnosed in the public sector.

Implications for Programs, Policy, and/or Research: Continued monitoring of HIV and syphilis trends is important to aid prevention programs in reaching populations at greater risk for co-infection and individuals in areas with an increased prevalence of both diseases.