1. Department of Pediatrics; National Hospital Organization Yokohama Medical Center; 3-60-2 Harajuku, Totsuka-ku Yokohama, Kanagawa 245-8575
2. Department of Pediatrics; Yokohama City University Graduate School of Medicine; 3-9 Fukuura, Kanazawa-ku Yokohama, Kanagawa 236-0004
3. Department of Health Science; Gunma Prefectural Institute of Public Health and Environmental Sciences; 378 Kamioki-machi Maebashi-shi, Gunma 371-0052
4. Infectious Disease Surveillance Center; National Institute of Infectious Diseases; 4-7-1, Gakuen Musashimurayama-shi, Tokyo 208-0011
5. Uchida-Y-Children's Clinic; 8 Totsuka-cho Totsuka-Ku; Yokohama Kanagawa 244-0003 Japan