1. David M. Morens and Jeffery K. Taubenberger are with the National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD. David M. Morens is Senior Adsvisor to the Director in the Office of the Director, and Jeffery K. Taubenberger is Chief, Viral Pathogenesis and Evolution Section, Laboratory of Infectious Diseases.