1. Department of Virology II; National Institute of Infectious Diseases; Musashi-murayama Tokyo 208-0011 Japan
2. Director-General, National Institute of Infectious Diseases; Toyama 1-23-1 Shinjuku-ku Tokyo 162-8640 Japan
3. Laboratory of Veterinary Public Health, Faculty of Agriculture; Tottori University; Tottori Tottori 680-8553 Japan