1. Department of Neurology, University of Florida, Gainesville
2. Department of Neurology, Yale School of Medicine, New Haven, Connecticut
3. Department of Medicine, University of California, Los Angeles
4. University of Texas Rio Grande Valley—Valley Baptist Medical Center—Harlingen
5. Riverside Methodist Hospital, Columbus, Ohio
6. Department of Neurology, Hospital of the University of Pennsylvania, Philadelphia
7. Centers for Disease Control and Prevention, Atlanta, Georgia