HIV Incidence Among Men Diagnosed with Early Syphilis in Atlanta, San Francisco, and Los Angeles, 2004 to 2005

Background: Syphilis outbreaks among men who have sex with men (MSM) in the United States have raised concerns about increased HIV transmission in this population. We sought to estimate HIV incidence among men diagnosed with primary or secondary (P&S) syphilis in sexually transmitted disease (STD) clinics in Atlanta, San Francisco, and Los Angeles.

Methods: We analyzed deidentified sociodemographic information from routine syphilis surveillance databases and matching remnant sera from consecutive male patients with P&S syphilis who were tested for syphilis at 3 public health laboratories during January 2004 through January 2006. Deidentified sera positive for Treponema pallidum by particle agglutination were screened for HIV-1 antibodies by enzyme immunoassay (EIA). Specimens that were confirmed HIV-positive by Western blot analysis were then tested for recent HIV infection using the less sensitive (LS) HIV-1 Vironostika EIA and BED HIV-specific IgG/total IgG assay.

Results: Of 357 men with P&S syphilis (98 in Atlanta, 151 in San Francisco, and 108 in Los Angeles), 32% had primary syphilis and 85% were MSM (12% no MSM risk and 3% no information). The median age was 36 years; 40% were white, 31% black, 20% Hispanic, and 8% other. Among men with P&S syphilis, 160 (45%) were HIV-positive, of whom 8 were classified as having acquired recent HIV infection by the LS-Vironostika EIA (all confirmed by BED) and had no history of antiretroviral use or HIV-positive results >6 months earlier. Seven of the 8 men with recent HIV infection were MSM. The estimated HIV incidence was 9.5% per year (95% confidence interval [CI]: 2.9 to 16.0) among all men and 10.5% per year (95% CI: 2.7 to 18.3) among MSM.

Conclusions: We found high HIV incidence among a high-risk population of US men diagnosed with P&S syphilis in STD clinics in Atlanta, San Francisco, and Los Angeles. Intensive integrated HIV/STD prevention programs are needed for this population.