Disease Burden of Influenza
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.
The preliminary cumulative burden estimates for the 2019-2020 season have been released. In-season preliminary burden estimates are scheduled to resume for the 2020-2021 season this winter.
Figure 1: Estimated Range of Annual Burden of Flu in the U.S. from 2010 – 2020
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 million – 45 million illnesses, between 140,000 – 810,000 hospitalizations and between 12,000 – 61,000 deaths annually since 2010.
Symptomatic Illnesses | Medical Visits | Hospitalizations | Deaths | |||||
---|---|---|---|---|---|---|---|---|
Season | Estimate | 95% U I | Estimate | 95% U I | Estimate | 95% U I | Estimate | 95% U 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 | 24,000,000 | (20,000,000 – 33,000,000) | 11,000,000 | (9,000,000 – 15,000,000) | 280,000 | (220,000 – 480,000) | 23,000 | (17,000 – 35,000) |
2016-2017 | 29,000,000 | (25,000,000 – 45,000,000) | 14,000,000 | (11,000,000 – 23,000,000) | 500,000 | (380,000 – 860,000) | 38,000 | (29,000 – 61,000) |
Preliminary estimates* | Estimate | 95% UI | Estimate | 95% UI | Estimate | 95% UI | Estimate | 95% UI |
2017-2018* | 45,000,000 | (39,000,000 – 58,000,000) | 21,000,000 | (18,000,000 – 27,000,000) | 810,000 | (620,000 – 1,400,000) | 61,000 | (46,000 – 95,000) |
2018-2019* | 36,000,000 | (31,000,000 – 45,000,000) | 17,000,000 | (14,000,000 – 21,000,000) | 490,000 | (390,000 – 770,000) | 34,000 | (26,000 – 53,000) |
2019-2020* | 38,000,000 | (34,000,000 – 47,000,000) | 18,000,000 | (15,000,000 – 22,000,000) | 400,000 | (350,000 – 500,000) | 22,000 | (18,000 – 29,000) |
* Estimates from the 2017-2018, 2018-2019, and 2019-2020 seasons are preliminary and may change as data are finalized.
Figure 2: Estimated U.S. Influenza Burden, By Season
Download Flu Burden PowerPoint Presentation Slides ppt icon[PPT – 1 MB]
Supporting Research
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 preparednessexternal icon. Influenza Other Respir Viruses. 2018
- Study: Estimating influenza disease burden from population-based surveillance data in the United States.external icon PLoS One. 2015
- Study: The US Influenza Hospitalization Surveillance Networkexternal icon. Emerg Infect Dis. 2015
- Study: Hospitalizations associated with influenza and respiratory syncytial virus in the United States, 1993-2008external icon. Clin Infect Dis. 2012
- Study: Influenza-associated hospitalizations in the United Statesexternal icon. JAMA. 2004
Global
- Study: Estimates of global seasonal influenza-associated respiratory mortality: a modelling studyexternal icon. 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 analysisexternal icon. 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.
- 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 Statesexternal icon. JAMA. 2003
Visit Flu Burden Averted by Vaccination for CDC estimates of flu-related deaths averted by vaccination.
- Study: The annual impact of seasonal influenza in the US: measuring disease burden and costsexternal icon. Vaccine. 2007
- CDC Foundation: Flu Prevention Infographic, “Business Challenges”external icon.