1. Bernard and Gloria Salick Equine Viral Disease Laboratory, Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, California 956161;
2. Division of Life Sciences, University of Texas at San Antonio, San Antonio, Texas 782492; and
3. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina 275993