1. a Department of International Health , Boston University School of Public Health , Crosstown 387, 801 Massachusetts Avenue, Boston , MA , 02118 , USA
2. b MRC/UVRI Uganda Research Unit on AIDS, Medical Research Council (UK)/Uganda , Virus Institute (UVRI) , PO Box 49, Entebbe , Uganda
3. c The AIDS Support Organisation , Old Mulago Complex, Kampala , Uganda
4. d London School of Hygiene & Tropical Medicine , Keppel Street, London , WC1E 7HT , UK