1. Department of Microbiology; College of Medicine, Korea University; 5-Ka, Anam-Dong Sungbuk-Ku Seoul 136-705 Korea
2. Institute for Viral Diseases; College of Medicine, Korea University; 5-Ka, Anam-Dong Sungbuk-Ku Seoul 136-705 Korea
3. Department of Pediatrics; College of Medicine, Korea University; 5-Ka, Anam-Dong Sungbuk-Ku Seoul 136-705 Korea
4. Korea National Institute of Health; Nokbun-dong; Eunpyung-ku Seoul 122-701 Korea