Seasonal Influenza Illness in the United States

Questions & Answers

How many people in the United States become sick with influenza illness in a typical year?

An online report published on December 9, 2016 estimated that from 2010-2011 to 2015-2016, flu-related hospitalizations in the United States ranged from a low of 140,000 (during 2011-2012) to a high of 710,000 (during 2014-2015). During the 2015-2016 flu season, CDC estimated that 310,000 people were hospitalized for flu-related illness.

What is the main lesson learned from annual estimates of annual influenza illness?

Seasonal influenza is associated with large numbers of hospitalizations. The results of this online report and previous studies demonstrate the substantial health impact of seasonal influenza and underscore the need to ensure vaccination of people at increased risk of serious influenza complications, especially people 65 years and older.

Why does CDC estimate annual influenza illness?


Can you provide more information about past studies on seasonal influenza illness?



  1. Simonsen L, Fukuda K, Schonberger LB, Cox NJ. The impact of influenza epidemics on hospitalizations. J Infect Dis. 2000;181(3):831-7. Available from: