[1] Natl Utano Hosp, Dept Neurol, Ukyo Ku, Kyoto 616, Japan
[2] Natl Utano Hosp, Clin Res Ctr, Ukyo Ku, Kyoto 616, Japan
[3] Kyoto Microbiol Inst, Kyoto 616, Japan
[4] Kyoto Univ, Inst Virus Res, Kyoto 616, Japan
[5] Kobe City Gen Hosp, Dept Paediat, Kobe, Hyogo, Japan
[6] Publ Hlth Res Inst Kobe City, Kobe, Hyogo, Japan