1. Department of Pediatrics, Columbia University Irving Medical Center , New York, New York , USA
2. Department of Infection Prevention & Control, New York-Presbyterian Hospital , New York, New York , USA
3. Division of Viral Diseases, Centers for Disease Control and Prevention , Atlanta, Georgia , USA
4. Columbia University School of Nursing , New York, New York , USA
5. Influenza Division, Centers for Disease Control and Prevention , Atlanta, Georgia , USA
6. United States Public Health Service , Rockville, Maryland , USA