1. Department of Internal Medicine and AIDS Research Institute, Yonsei University College of Medicine, Seoul, Korea.
2. Department of Preventive Medicine, Hanyang University College of Medicine, Seoul, Korea.
3. 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. Division of Infectious Disease, Department of Internal Medicine, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
6. Division of Viral Disease Research, Center for Infectious Diseases Research, Korea, National Institute of Health, Cheongju, Korea.