1. Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
2. Division of Infectious Disease, Department of Internal Medicine, College of Medicine, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Korea.
3. Division of Infectious Disease, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
4. Department of Internal Medicine, School of Medicine, Kyungpook National University, Daegu, Korea.
5. Department of Internal Medicine, Inha University School of Medicine, Incheon, Korea.
6. Department of Preventive Medicine, Hanyang University College of Medicine, Seoul, Korea.
7. Institute for Health and Society, Hanyang University, Seoul, Korea.
8. Korea Centers for Disease Control and Prevention, Cheongju, Korea.