1. Department of Clinical SciencesLiverpool School of Tropical Medicine, Liverpool, UK
2. Department of Environmental HealthRollins School of Public Health, Emory University, Atlanta, GA, USA
3. Department of Disease ControlLondon School of Hygiene and Tropical Medicine, London, UK
4. WASH SectionProgramme Division, United Nations Children Fund, New York, NY, USA
5. Department of Sociomedical SciencesColumbia University Mailman School of Public Health, New York, NY, USA