1. a Environmental Health and WASH, Health System and Population Studies Division, icddr,b, 68, Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka 1212, Bangladesh
2. b School of Public Health and Preventive Medicine, Monash University, Level 1, 553 St Kilda Road, Melbourne, Victoria, Australia 3004
3. c Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Room E5608, Baltimore, MD 21205, USA
4. d Infectious Diseases and Geographic Medicine, Stanford University, 473 Via Ortega, Stanford, CA 94305, USA