Circular migration by Mexican female sex workers who are injection drug users: implications for HIV in Mexican sending communities.

Circular migration and injection drug use increase the risk of HIV transmission in sending communities. We describe female sex workers who are injection drug users' (FSW-IDUs) circular migration and drug use behaviors. Between 2008-2010, 258 migrant FSW-IDUs residing in Tijuana and Ciudad Juarez, Mexico responded to questionnaires. 24% of FSW-IDUs were circular migrants. HIV prevalence was 3.2% in circular migrants and 6.1% in non-circular migrants; 50% of circular and 75% of non-circular migrants were unaware of their HIV infection. Among circular migrants, 44% (n = 27) consumed illicit drugs in their birthplace; 74% of these (n = 20) injected drugs and one-half of injectors shared injection equipment in their birthplace. Women reporting active social relationships were significantly more likely to return home. Circular migrant FSW-IDUs exhibit multiple HIV risks and opportunities for bridging populations. Regular HIV testing and treatment and access to substance use services is critical for FSW-IDUs and their sexual/drug-using contacts.