1. Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention , Atlanta, Georgia , USA
2. Epidemic Intelligence Service, Centers for Disease Control and Prevention , Atlanta, Georgia , USA
3. Massachusetts Department of Public Health , Boston, Massachusetts , USA
4. Boston Health Care for the Homeless Program , Boston, Massachusetts , USA
5. Public Health Division, Oregon Health Authority , Portland, Oregon , USA
6. Colorado Department of Public Health and Environment , Denver, Colorado , USA