Characteristics of female sex workers with US clients in two Mexico-US border cities.

Background: HIV prevalence is increasing among female sex workers (FSWs) in Tijuana and Ciudad Juarez, 2 Mexican cities on the US border. Quasilegal prostitution in both cities attracts large numbers of sex tourists. We compared FSWs with and without US clients in both cities.
Methods: FSWs aged > or =18 years reporting unprotected sex with > or =1 client within the last 2 months, who were not knowingly HIV-infected, were enrolled in a behavioral intervention study. At baseline, participants underwent interviews, antibody testing for HIV and syphilis, and vaginal swabs for detecting gonorrhea and Chlamydia. Logistic regression identified factors associated with reporting >1 US client.
Results: Of 924 FSWs, 69% had US clients. Median age and duration in sex work were 32 and 4 years. Prevalence of HIV, infectious syphilis (titer > or =1:8), gonorrhea, Chlamydia, and any STI was 6%, 14%, 6%, 13%, and 27%, respectively. Compared with other FSWs, FSWs with US clients were more likely to have syphilis titers > or =1:8 (16% vs. 10%, P = 0.01), gonorrhea (8% vs. 2%, P <0.001) or any STI, including HIV (30% vs. 20%, P = 0.002). Factors independently associated with having US clients were: living in Tijuana, being younger, speaking English, being paid more for having sex without a condom, having >250 clients in the last 6 months, having syphilis titers > or =1:8, and injecting drugs.
Conclusions: In these border cities, FSWs reporting US clients were more likely to have current STIs and to engage in higher-risk behaviors. Intensified binational prevention efforts involving both FSWs and their clients are urgently needed.