Nutrition and Clinical Services Division, International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka 1212, Bangladesh. mislam@icddrb.org. Children's Hospital Oakland Research Institute, Oakland, CA 94609, USA. chmcdonald@chori.org. Department of Pediatrics, University of Colorado Denver Anschutz Medical Campus, Aurora, CO 80045, USA. Nancy.Krebs@ucdenver.edu. Department of Pediatrics, University of Colorado Denver Anschutz Medical Campus, Aurora, CO 80045, USA. Jamie.Westcott@ucdenver.edu. Maternal and Child Health Division, International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka 1212, Bangladesh. ehsanur@icddrb.org. Maternal and Child Health Division, International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka 1212, Bangladesh. shams@icddrb.org. Nutrition and Clinical Services Division, International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka 1212, Bangladesh. tahmeed@icddrb.org. Children's Hospital Oakland Research Institute, Oakland, CA 94609, USA. jking@chori.org. Institute for International Programs, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA. rblack1@jhu.edu.