1. Department of Pediatrics; Asahikawa Medical University; Hokkaido Japan
2. Ujiie Memorial Clinic for Children; Hokkaido Japan
3. Department of Pediatrics; Kobe University Graduate School of Medicine; Hyogo Japan
4. Department of Pediatrics; Tokyo University; Tokyo Japan
5. Department of Pediatrics; Nagasaki University; Nagasaki Japan
6. Department of Obstetrics and Gynecology; Fukushima Medical University; Fukushima Japan
7. Department of Maternal and Perinatal Services; National Center for Child Health and Development; Tokyo Japan
8. Department of Pediatrics; Fujita Health University; Aichi Japan
9. Department of Obstetrics and Gynecology; Kobe University Graduate School of Medicine; Hyogo Japan
10. Department of Microbiology; Fukushima Medical University; Fukushima Japan
11. Department of Virology I; National Institute of Infectious Diseases; Tokyo Japan
12. Department of Microbiology and Immunology; Gifu Pharmaceutical University; Gifu Japan