1. From the Department of Social Medicine, National Center for Child Health and Development, Tokyo, Japan
2. Department of Pediatrics, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Science, Okayama, Japan
3. Department of Pediatrics, Hamamatsu University School of Medicine, Shizuoka, Japan
4. Department of Microbiology, Immunology, and Biochemistry, University of Tennessee Health Science Center, Memphis, Tennessee.