BACKGROUND: Recent increases syphilis are especially concerning, given the biologic and epidemiologic associations between syphilis and HIV infection. The Centers for Disease Control and Prevention (CDC) has previously reported national data on primary and secondary (P&S) syphilis and HIV co-infection among men who have sex with men (MSM), men who have sex with women only (MSW), and women. However, national data on P&S syphilis and HIV co-infection among demographic groups such as race/ethnicity groups and age groups have not previously been described.
METHODS: P&S syphilis case report data from 2015, including available risk factor information such as sex of sex partner and HIV status, were extracted from the National Electronic Telecommunications System for Surveillance, the system through which CDC receives notifiable STD data from all 50 states and the District of Columbia. The proportion of P&S syphilis cases with HIV co-infection was calculated using cases with known HIV status (either known to be living with HIV or known to be HIV-negative) as the denominator and were examined by demographic group and by reported sex/sex of sex partner (MSM, MSW, and women).
RESULTS: In 2015, there were 23,872 reported cases of P&S syphilis in the United States. Of the 15,742 (65.9%) cases reported with known HIV status, 6,453 (41.0%) were co-infected with HIV. The proportion of cases with HIV co-infection was higher among male cases (44.9%) compared with female cases (3.5%). Among male cases with known sex of sex partner, the prevalence of HIV co-infection was higher among MSM (49.3%) than MSW (10.3%). Among MSM, the proportion of P&S syphilis cases with HIV co-infection was highest among non-Hispanic blacks (62.7%) compared with non-Hispanic whites (43.4%) and Hispanics (43.0%). The proportion with co-infection increased with increasing age from 18.2% among MSM cases aged 15–19 years to 65.1% among MSM cases aged 40–44 years, but declined to 63.7% among MSM cases aged 45–49 years and 56.3% among MSM cases aged ≥50 years.
CONCLUSIONS: These data underscore the epidemiologic linkages between syphilis and HIV, particularly among MSM. Because P&S syphilis may be an indication of condomless sexual contact within sexual networks at high risk of HIV transmission, a diagnosis of P&S syphilis may represent a public health and clinical opportunity to (1) prevent HIV infection among those who are HIV-negative and (2) identify and link to care those who are living with HIV infection but not currently engaged in care.