Disease Burden of Influenza
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Each year CDC estimates the burden of influenza in the U.S. CDC uses modeling to estimate the number of influenza illnesses, medical visits, flu-associated hospitalizations, and flu-associated deaths that occur in the U.S. in a given season. The methods used to calculate these estimates are described on CDC’s webpage, How CDC Estimates the Burden of Seasonal Influenza in the U.S.
CDC uses the estimates of the burden of influenza in the population and the impact of influenza vaccination to inform policy and communications related to influenza.
2017-2018 Flu Season Burden Estimates
CDC calculates estimates of disease burden in the United States using surveillance data and modeling to adjust for sources of under-detection.
How CDC Estimates the Burden of Flu
CDC uses modeling to estimate the number of influenza illnesses, medical visits, flu-associated hospitalizations, and flu-associated deaths that occur in the U.S. in a given season.
Why CDC Estimates the Burden of Flu
CDC uses the estimates of the burden of influenza in the population and the impact of influenza vaccination to inform policy and communications related to influenza.
Estimated Range of Annual Burden of Flu in the U.S. since 2010
The burden of influenza disease in the United States can vary widely and is determined by a number of factors including the characteristics of circulating viruses, the timing of the season, how well the vaccine is working to protect against illness, and how many people got vaccinated. While the impact of flu varies, it places a substantial burden on the health of people in the United States each year.
CDC estimates that influenza has resulted in between 9.3 million – 49.0 million illnesses, between 140,000 – 960,000 hospitalizations and between 12,000 – 79,000 deaths annually since 2010.
| Symptomatic Illnesses | Medical Visits | Hospitalizations | Deaths | |||||
|---|---|---|---|---|---|---|---|---|
| Season | Estimate | 95% Cr I | Estimate | 95% Cr I | Estimate | 95% Cr I | Estimate | 95% Cr I |
| 2010-2011 | 21,000,000 | (20,000,000 – 25,000,000) | 10,000,000 | (9,300,000 – 12,000,000) | 290,000 | (270,000 – 350,000) | 37,000 | (32,000 – 51,000) |
| 2011-2012 | 9,300,000 | (8,700,000 – 12,000,000) | 4,300,000 | (4,000,000 – 5,600,000) | 140,000 | (130,000 – 190,000) | 12,000 | (11,000 – 23,000) |
| 2012-2013 | 34,000,000 | (32,000,000 – 38,000,000) | 16,000,000 | (15,000,000 – 18,000,000) | 570,000 | (530,000 – 680,000) | 43,000 | (37,000 – 57,000) |
| 2013-2014 | 30,000,000 | (28,000,000 – 33,000,000) | 13,000,000 | (12,000,000 – 15,000,000) | 350,000 | (320,000 – 390,000) | 38,000 | (33,000 – 50,000) |
| 2014-2015 | 30,000,000 | (29,000,000 – 33,000,000) | 14,000,000 | (13,000,000 – 16,000,000) | 590,000 | (540,000 – 680,000) | 51,000 | (44,000 – 64,000) |
| 2015-2016 * | 25,000,000 | (24,000,000 – 28,000,000) | 12,000,000 | (11,000,000 – 13,000,000) | 310,000 | (290,000 – 340,000) | 25,000 | (21,000 – 31,000) |
| 2016-2017 * | 30,000,000 | (28,000,000 – 32,000,000) | 14,000,000 | (13,000,000 – 16,000,000) | 580,000 | (520,000 – 660,000) | 51,000 | (44,000 – 64,000) |
| 2017-2018 * | 49,000,000 | (46,000,000 – 53,000,000) | 23,000,000 | (21,000,000 – 25,000,000) | 960,000 | (870,000 – 1,100,000) | 79,000 | (69,000 – 99,000) |
* Estimates from the 2015-2016, 2016-2017, and 2017-2018 seasons are preliminary and may change as data are finalized.
Supporting Research
Flu-related illness and hospitalization
United States
- Q&A: Seasonal Influenza-Associated Hospitalizations in the United States.
- Study: Annual estimates of the burden of seasonal influenza in the United States: A tool for strengthening influenza surveillance and preparedness. Influenza Other Respir Viruses. 2018
- Study: Estimating influenza disease burden from population-based surveillance data in the United States. PLoS One. 2015
- Study: The US Influenza Hospitalization Surveillance Network. Emerg Infect Dis. 2015
- Study: Hospitalizations associated with influenza and respiratory syncytial virus in the United States, 1993-2008. Clin Infect Dis. 2012
- Study: Influenza-associated hospitalizations in the United States. JAMA. 2004
Global
- Study: Estimates of global seasonal influenza-associated respiratory mortality: a modelling study. Lancet. 2017
- Web article: Seasonal flu death estimate increases worldwide.
- Study: Global role and burden of influenza in pediatric respiratory hospitalizations, 1982-2012: A systematic analysis. PLoS Med. 2016
- Web article: CDC Collaborative Study: Influenza Important Cause of Respiratory Hospitalizations Worldwide.
Visit Flu Burden Averted by Vaccination for CDC estimates of flu-related illness and hospitalization averted by vaccination.
Flu-related deaths
- Q&A: Estimating Seasonal Influenza-Associated Deaths in the United States: CDC Study Confirms Variability of Flu.
- Background on CDC web site: Under-counting of Flu-related Deaths.
- Study: Estimates of deaths associated with seasonal influenza—United States, 1976–2007. MMWR. 2010
- Study: Mortality associated with influenza and respiratory syncytial virus in the United States. JAMA. 2003
Visit Flu Burden Averted by Vaccination for CDC estimates of flu-related deaths averted by vaccination.
Economic impact of influenza
- Study: The annual impact of seasonal influenza in the US: measuring disease burden and costs. Vaccine. 2007
- CDC Foundation: Flu Prevention Infographic, “Business Challenges”.
More Information
- Page last reviewed: October 25, 2018
- Page last updated: October 25, 2018
- Content source:
- Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases (NCIRD)
- Page maintained by: Office of the Associate Director for Communication, Digital Media Branch, Division of Public Affairs