1. Department of Infectious Diseases, Respiratory, and Digestive Medicine, Graduate School of Medicine, University of the Ryukyus, Okinawa, Japan
2. Personnel Health Management Center, Department of General Affairs, Okinawa Prefectural Government, Japan
3. Department of Respiratory Medicine, Okinawa Chubu Hospital, Japan
4. Virus Research Center, Sendai Medical Center, National Hospital Organization, Miyagi, Japan
5. Department of Virology, Tohoku University Graduate School of Medicine, Miyagi, Japan