1. Division of Infectious Diseases, Department of Internal Medicine, Chungbuk National University Hospital, Cheongju, Korea.
2. Department of Internal Medicine, The Armed Forces Capital Hospital, Seongnam, Korea.
3. Department of Preventive Medicine, The Armed Forces Medical Command, Seongnam, Korea.
4. Division of Infectious Diseases, Department of Internal Medicine, Korea University Kuro Hospital, Seoul, Korea.