1. Viral and Rickettsial Zoonoses Branch, Division of Viral and Rickettsial Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia
2. Washington and Jefferson College, Washington
3. Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado
4. School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania