1. Nutrition and Clinical Services Division, International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka 1212, Bangladesh
2. Department of Pathology, Bangladesh Specialized Hospital, Dhaka 1207, Bangladesh
3. Department of Gastroenterology, Dhaka Medical College and Hospital, Dhaka 1000, Bangladesh
4. Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, VA 22908, USA