1. Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639
2. CREST, Japan Science and Technology Corporation, Saitama 332-0012, Japan
3. Special Pathogens Program, National Microbiology Laboratory, Canadian Science Centre for Human and Animal Health, Winnipeg, Manitoba R3E 3R2, Canada
4. Special Pathogens Branch, Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333
5. Department of Pathobiological Sciences, University of Wisconsin, Madison, Wisconsin 53706