1. Department of Virology; University of the Ryukyus; Okinawa 903-01 Japan
2. Research Center of Comprehensive Medicine, Faculty of Medicine; University of the Ryukyus; Okinawa 903-01 Japan
3. Department of Microbiology, Faculty of Medicine; Chiang Mai University; Chiang Mai Thailand
4. Department of Pediatrics, Faculty of Medicine; Chiang Mai University; Chiang Mai Thailand