1. Arctic Investigations Program, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Public Health Service, U.S. Department of Health and Human Services, Anchorage, Alaska,1 and
2. Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention,2 and
3. Division of Pediatric Gastroenterology and Nutrition, Department of Pediatrics, Emory University School of Medicine,3 Atlanta, Georgia