1. Department of Microbiology and Immunology, National Defense Medical Center, Taipei 114, Taiwan
2. Department of Otolaryngology-Head & Neck Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 114, Taiwan
3. Division of Infectious Diseases and Tropical Medicine, Department of Internal Medicine, Tri-Service General Hospital, Taipei 114, Taiwan
4. Department of Internal Medicine, Tri-Service General Hospital, Taipei 114, Taiwan