[1] Natl Inst Infect Dis, Dept Virol 2, Musashino, Tokyo 2080011, Japan
[2] Yamaguchi Prefectural Res Inst Publ Hlth, Yamaguchi, Japan
[3] Hiroshima City Inst Publ Hlth, Hiroshima, Japan
[4] Tohoku Univ, Sendai, Miyagi 980, Japan
[5] Miyagi Prefectural Inst Publ Hlth & Environm, Sendai, Miyagi 980, Japan