1. Department of Internal Medicine, Konyang University College of Medicine, Daejeon, Korea.
2. Department of Internal Medicine, Guro Hospital, Korea University College of Medicine, Seoul, Korea.
3. Department of Internal Medicine, Kangnam Sacred Heart Hospital, Hallym University School of Medicine, Seoul, Korea.
4. Department of Internal Medicine, Inha University College of Medicine, Incheon, Korea.
5. Department of Internal Medicine, St. Vincent's Hospital, School of Medicine, The Catholic University of Korea, Suwon, Korea.
6. Department of Internal Medicine, Chungbuk National University College of Medicine, Cheongju, Korea.
7. Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
8. Department of Internal Medicine, Chonnam National University School of Medicine, Kwangju, Korea.
9. Department of Internal Medicine, Kyungpook National University School of Medicine, Daegu, Korea.
10. Department of Internal Medicine, Pusan National University School of Medicine, Busan, Korea.
11. Department of Internal Medicine, Ansan Hospital, Korea University College of Medicine, Ansan, Korea.
12. Transgovernmental Enterprise for Pandemic Influenza in Korea, Seoul, Korea.