1. Research Center for Drug and Vaccine Development, National Institute of Infectious Diseases, Tokyo 162-8640, Japan.
2. Department of Virology I, National Institute of Infectious Diseases, Tokyo 162-8640, Japan.
3. Tokyo Shinagawa Hospital, Tokyo 140-8522, Japan.
4. Department of Pediatrics, Showa General Hospital, Tokyo 187-8510, Japan.
5. Department of Infectious Diseases, Tokyo Metropolitan Bokutoh Hospital, Tokyo 130-8575, Japan.
6. Department of Respiratory Medicine, JCHO Tokyo Shinjuku Medical Center, Tokyo 162-0821, Japan.
7. Department of Pathology, National Institute of Infectious Diseases, Tokyo 162-8640, Japan.