1. Departments of Medical Microbiology1 and
2. Internal Medicine,2 University of Manitoba, Winnipeg, Manitoba R3E 0W3, Canada;
3. Departments of Neurology3 and
4. Epidemiology,4 Johns Hopkins University, Baltimore, Maryland 21287;
5. Department of Neurology, University of Kentucky, Lexington, Kentucky 405365; and
6. Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 598406