1. Department of Pediatrics, University of Iowa College of Medicine, Iowa City, IA, USA
2. Department of Microbiology, Biomedical Sciences Institute, University of São Paulo, 05508-000 São Paulo, Brazil
3. Internal Medicine, University of Iowa College of Medicine, Iowa City, IA, USA
4. International Centre for Diarrheal Disease Research, Bangladesh (ICDDR,B), Dhaka, Bangladesh
5. Departments of Biology and Microbiology, and Veterinary and Biomedical Sciences, South Dakota State University, Brookings, SD, USA