1. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
2. Department of Neurology, Yonsei University College of Medicine, Seoul, Korea.
3. The Armed Forces Medical Command, Seongnam, Korea.
4. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Armed Forces Capital Hospital, Seongnam, Korea.
5. Division of Infectious Diseases, Department of Internal Medicine, Armed Forces Capital Hospital, Seongnam, Korea.