1. Division of Infectious Diseases, National Medical Center, Seoul, Korea.
2. Department of Internal Medicine, National Medical Center, Seoul, Korea.
3. Department of Pediatrics, National Medical Center, Seoul, Korea.
4. Research Institute of Public Health, National Medical Center, Seoul, Korea.
5. National Institute of Infectious Diseases, National Institute of Health, Korea Disease Control and Prevention Agency, Cheongju, Korea.
6. Division of Infectious Diseases, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, Seoul, Korea.