1. Virology Division, Department of Laboratory Medicine, University of Washington, Seattle, WA 98104.
2. Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390.
3. Department of Surgery, University of Pittsburgh, Pittsburgh, PA 15260.
4. Lady David Institute-Jewish General Hospital, Departments of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada.
5. Virology Division, Departments of Laboratory Medicine and Medicine, University of Washington, Seattle, WA 98104.
6. Virology Division, Departments of Laboratory Medicine and Microbiology, University of Washington, Seattle, WA 98104.