1. Division of Infectious Diseases and Respiratory Medicine, Department of Internal Medicine, National Defense Medical College, Saitama, Japan.
2. Department of General Medicine, National Defense Medical College, Saitama, Japan.
3. Department of Pathology and Laboratory Medicine, National Defense Medical College, Saitama, Japan.
4. Department of General Medical Practice and Laboratory Diagnostic Medicine, Akita University Graduate School of Medicine, Akita, Japan.