[1] Pediat Allergy & Infect Dis Soc Sapporo, Kumagai Pediat Clin, Atsubetsu Ku, Sapporo, Hokkaido 0040013, Japan
[2] Sapporo Med Univ, Sch Med, Dept Pediat, Chuo Ku, Sapporo, Hokkaido 0600061, Japan
[3] Hokkaido Inst Publ Hlth, Kita Ku, Sapporo, Hokkaido 0600819, Japan
[4] Kitasato Inst Life Sci, Lab Viral Infect 1, Minato Ku, Tokyo 1088462, Japan
[5] Osaka Inst Publ Hlth, Higashinari Ku, Osaka 5370025, Japan
[6] Mie Natl Hosp, Dept Pediat, Tsu, Mie 5140125, Japan