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
3. Special Pathogens Program, National Microbiology Laboratory, Canadian Science Centre for Human and Animal Health, Winnipeg, Manitoba R3E 3R2, Canada
4. Institute for Virology, Philipps-University, Marburg, Germany
5. Division of Virology and Pathology, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland 21702-5011
6. Department of Pathobiological Sciences, University of Wisconsin, Madison, Wisconsin 53706
7. Department of Veterinary Public Health, Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan