1. Department of Virology, Institute of Medical Science, University of Tokyo , Tokyo , Japan
2. International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo , Tokyo , Japan
3. Division of Infectious Diseases, Advanced Clinical Research Center, Institute of Medical Science, University of Tokyo , Tokyo , Japan
4. Department of Infectious Diseases and Applied Immunology, IMSUT Hospital of Institute of Medical Science, the University of Tokyo , Tokyo , Japan
5. Tokyo Health Cooperative Association, Nezu Clinic , Tokyo , Japan
6. Department of Infectious Diseases, The University of Tokyo Hospital , Tokyo , Japan
7. The Research Center for Global Viral Diseases, National Center for Global Health and Medicine Research Institute , Tokyo , Japan
8. Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison , Madison, Wisconsin , USA