1. Department of Disease Control, London School of Hygiene & Tropical Medicine, London, England.
2. Sanford School of Public Policy, Duke University, Durham, United States of America (USA).
3. Water, Sanitation and Health Unit, World Health Organization, Geneva, Switzerland.
4. School of Civil and Environmental Engineering, Georgia Institute of Technology, Mason Building, 790 Atlantic Drive, Atlanta, GA 30332-0355, USA.