1. Program in Public Health and Department of Family, Population and Preventive Medicine, State University of New York at Stony Brook, Stony Brook, NY, USA
2. State University of New York at Stony Brook, Stony Brook, NY, USA
3. Work completed while with the Department of Family, Population and Preventive Medicine, State University of New York at Stony Brook, Stony Brook, NY, USA
4. Perinatal HIV Research Unit (PHRU), Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa