[1] Yamagata Univ, Sch Med, Dept Infect Dis, Fac Med, Yamagata 9909585, Japan
[2] Kanazawa Med Univ, Sch Med, Dept Microbiol, Uchinada, Ishikawa 9200293, Japan
[3] Mitsubishi Chem Medience Corp, Drug Anal Dept, Kashima Lab, Div Toxicol Sci,Medi Chem Business Segment, Kamisu City, Ibaraki 3140255, Japan
[4] Natl Inst Infect Dis, Influenza Virus Res Ctr, Tokyo 2080011, Japan