1. Department of Pathology, National Institute of Infectious Diseases, 208-0011 Tokyo, Japan.
2. Pathogen Genomics Center, National Institute of Infectious Diseases, 162-8640 Tokyo, Japan.
3. Department of Biological Science and Technology, Tokyo University of Science, 125-8585 Tokyo, Japan.
4. Influenza Virus Research Center, National Institute of Infectious Diseases, 208-0011 Tokyo, Japan.