Transmission of primary and secondary syphilis by oral sex--Chicago, Illinois, 1998-2002.

During 1998-2002, the STD/HIV Prevention and Care Program of the Chicago Department of Public Health (CDPH) recorded 1,582 cases of primary and secondary (P&S) syphilis, the most of any U.S. city. Although case numbers and overall rates remained stable in Chicago during this period, patterns of transmission changed substantially. Throughout most of the 1990s, P&S syphilis was reported almost exclusively among heterosexuals. During 1998-2000, however, men who have sex with men (MSM) accounted for approximately 15% of Chicago's P&S syphilis morbidity. Since 2001, MSM have accounted for nearly 60% of patients with P&S syphilis. During 2000-2002, CDPH conducted interviews with persons with syphilis; some MSM reported they had engaged in only oral sex and were surprised to have acquired syphilis. In response, CDPH began collecting information on oral sex from persons with syphilis. To assess the role of oral sex in the transmission of P&S syphilis in Chicago, CDPH analyzed surveillance data and interview responses. This report summarizes the results of these analyses, which suggested that a substantial proportion (13.7%) of syphilis cases were attributed to oral sex, particularly among MSM. Persons who are not in a long-term monogamous relationship and who engage in oral sex should use barrier protection (e.g., male condoms or other barrier methods) to reduce the risk for sexually transmitted disease (STD) transmission.