1. Division of Infectious Diseases, Department of Medicine, Imperial College London, London W2 1PG, United Kingdom;
2. Laboratory of Virus Control, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto 606-8507, Japan
3. Department of Hematology, Rheumatology and Infectious Diseases, Kumamoto University School of Medicine, Kumamoto 860-8556, Japan;