1. Department of Emergency Medicine, Seoul National University College of Medicine, Seoul, Korea.
2. Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
3. Infection Control Service, Seoul National University Hospital, Seoul, Korea.
4. Department of Clinical Laboratory, Seoul National University Hospital, Seoul, Korea.
5. Department of Occupational & Environmental Health, Seoul National University Graduate School of Public Health, Seoul, Korea.
6. Department of Emergency Medicine, Singapore General Hospital, Singapore.