1. Department of Medical Microbiology, Stanford University, Stanford, CA 94305.
2. Nuffield Departments of Clinical Medicine and Surgery, John Radcliffe Hospital, University of Oxford, Oxford, England OX3 9DU.
3. Department of Medical Microbiology and Division of Oncology, Stanford University, Stanford, CA 94305.
4. Department of Neurology, Stanford University, Stanford, CA 94305.