1. Infectious Diseases Division, icddr,b (International Centre for Diarrhoeal Disease Research, Bangladesh), Dhaka, Bangladesh
2. Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
3. Maternal and Child Health Division, icddr,b, Dhaka, Bangladesh
4. Department of Clinical Trial and Clinical Epidemiology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan