1. Division of STD Prevention (DSTDP), International Activities Unit, U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Rd, NE, MS E-02, Atlanta, GA 30333, USA
2. Department of Reproductive Health and Research, World Health Organization (WHO), Geneva, Switzerland
3. Division of Global HIV/AIDS, CDC, Atlanta, GA, USA
4. University College London, London, UK