1. Division of Infectious Diseases, Department of Internal Medicine, Seoul Medical Center, Seoul, Korea.
2. Division of Infectious Diseases, Department of Internal Medicine, Ajou University School of Medicine, Suwon, Korea.
3. Division of Infectious Diseases, Department of Internal Medicine, Korea University Guro Hospital, Seoul, Korea.
4. Division of Infectious Diseases, Department of Internal Medicine, Korea University Ansan Hospital, Ansan, Korea.