1. Division of Virology; Kawasaki City Institute for Public Health; 3-25-13 Tonomachi, Kawasaki-ku Kawasaki-shi, Kanagawa 210-0821 Japan
2. Ibaraki Prefectural Institute of Public Health; 993-2 Kasaharacho, Mito-shi Ibaraki 310-0852 Japan
3. Tochigi Prefectural Institute of Public Health and Environmental Science; 2145-13 Shimookamotocho, Utsunomiya-shi Tochigi 329-1196 Japan
4. Infectious Disease Surveillance Center; National Institute of Infectious Diseases; 4-7-1 Gakuen, Musashimurayama-shi Tokyo 208-0011 Japan
5. Department of Microbiology; Yokohama City University School of Medicine; 3-9 Fuku-ura, Kanazawa-ku Yokohama-shi, Kanagawa 236-0004 Japan
6. Department of Virology III; National Institute of Infectious Diseases; 4-7-1 Gakuen Musashimurayama-shi, Tokyo 208-0011 Japan