1. Department of Viral Infection and International Health, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8640, Japan
2. Laboratory of Hematology and Virology, Faculty of Medicine and Biomedical Sciences, University of Yaounde-I, Yaounde 812, Cameroon
3. Laboratory of Viral Pathogenesis, Institute for Virus Research, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan