1 Division of Infectious Diseases, Department of Medical Specialties, National Center for Child Health and Development, Tokyo, Japan.
2 Division of Infectious Diseases, Department of Medical Specialties, National Center for Child Health and Development, Tokyo, Japan; Department of Microbiology, Immunology, and Biochemistry, University of Tennessee Health Science Center, Memphis, TN, USA. Electronic address: miyairi-i@ncchd.go.jp.