1. Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
2. Department of Infectious Diseases, Guro Hospital, Korea University College of Medicine, Seoul, Korea.
3. Department of Infectious Diseases, Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul, Korea.
4. Center for Infectious Diseases, National Medical Center, Seoul, Korea.