1. Department of Population Health, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, England.
2. Malawi Epidemiology and Intervention Research Unit, Lilongwe, Malawi.
3. MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), School of Public Health, University of the Witwatersrand, South Africa.
4. School of Nursing and Public Health, University of KwaZulu-Natal, Durban, South Africa.
5. Ministry of Health, Community Development, Gender, Elderly and Children, Dodoma, United Republic of Tanzania.
6. Ministry of Health, Lilongwe, Malawi.
7. National Institute of Medical Research, Mwanza, Tanzania.