1. Division of Infectious Disease and Center for Global Health, Massachusetts General Hospital, Boston, MA 02114, USA
2. Harvard Medical School, Boston, MA 02115, USA
3. Division of Infectious Disease, Beth Israel Deaconess Medical Center, Boston, MA 02115, USA
4. McCord Hospital, PMTCT Programme, Durban 4001, South Africa
5. Faculty of Arts and Sciences, Simon Fraser University, Vancouver, BC, Canada V6B 5K3
6. Department of Psychiatry, Massachusetts General Hospital, Boston, MA 02114, USA
7. Department of Global Health and Social Medicine, Harvard Medical School, Boston, MA 02115, USA
8. Maternal, Adolescent, Child Health Division, University of the Witwatersrand, Durban 4110, South Africa