1. Department of Rehabilitation Medicine, Armed Forces Yangju Hospital, Yangju, Korea.
2. Division of Respiratory and Critical Care Medicine, Department of Internal Medicine, Armed Forces Daejeon Hospital, Daejeon, Korea.
3. Division of Infectious Disease, Department of Internal Medicine, Armed Forces Capital Hospital, Seongnam, Korea.
4. Division of Infectious Disease, Department of Internal Medicine, Myongji Hospital, Goyang, Korea.