Background:
Despite recent expansion of syphilis control efforts, there has not been a U.S. population-based measure of syphilis prevalence in 25 years.

Objective:
To determine the prevalence of positive serologic tests for syphilis among a representative sample of the U.S. population.

Method:
Sera from 18-49 year-old participants in the 2001-2002 National Health and Nutrition Examination Survey (NHANES) were tested for syphilis IgG antibody using the syphilis-G enzyme immunoassay (EIA). Specimens with positive or indeterminate EIAs underwent rapid plasma reagin (RPR) testing. Specimens with RPR titers ≥1:8 were considered positive (more likely recent infection). Specimens with RPR titers <1:8 underwent confirmatory testing with Treponema pallidum particle agglutination (TP-PA); positive results were considered evidence of likely remote infection. Specimens with a negative EIA or TP-PA were considered negative for recent or remote syphilis.

Result:
Sera were available for 3028 participants. EIA testing was positive or indeterminate for 63, of which 5 (7.9%) had RPR titers ≥1:8. Of the remaining 58 specimens, 34 (58.6%) had positive TP-PA tests. Weighted prevalence of likely recent (RPR titer ≥1:8) syphilis infection was 0.06% and of likely remote (RPR titer <1:8) infection was 0.61%. Overall prevalence (recent or remote infection) was similar among males (0.67%) and females (0.68%) and increased with age (p=0.002), less education (p=0.02), and lower income (p=0.004). Non-Hispanic blacks had the highest prevalence (4.8%), followed by Mexican Americans (0.86%) and non-Hispanic whites (0%; p=0.002). Prevalence was 2.4% among those reporting non-heterosexual identity, versus 0.51% among heterosexuals (p=0.002).

Conclusion:
Consistent with surveillance data, this nationally representative survey shows substantial disparities in syphilis by race/ethnicity and sexual orientation.

Implications:
Further efforts are needed to reduce disparities in syphilis in the U.S.