1. From the Rabies Laboratory, Viral and Rickettsial Zoonoses Branch, Division of Viral and Rickettsial Diseases, Center for Infectious Diseases, Centers for Disease Control, Atlanta (J.S.S., D.B.F.); the Rabies Unit, Wistar Institute of Anatomy and Biology, Philadelphia (C.E.R.); and the Division of Zoonoses Control, Texas State Health Department, Austin (K.C.). Address reprint requests to Dr. Smith at the Rabies Laboratory, Mailstop G-33. Bldg. 15 SSB 611, Centers for Disease Control, Atlanta, GA 30333.