1. 1Department of Human Services, Oregon Health Division, Portland, Oregon 97232
2. 2Foodborne and Diarrheal Diseases Branch, Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia
3. 3California State Department of Health Services, Berkeley, California
4. 4Yale University, New Haven, Connecticut
5. 5Division of Public Health, Georgia Department of Human Resources, Atlanta, Georgia
6. 6Minnesota Department of Public Health, Minneapolis, Minnesota, USA