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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.

Classifying Flu Severity

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.

Flu-Associated Hospitalizations

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.

Flu-Associated Deaths

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.

Figure 1: Estimated Range of Annual Burden of Flu in the U.S. since 2010

Image: Flu burden cases

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.

Table 1: Estimated Influenza Disease Burden, by Season — United States, 2010-11 through 2017-18 Influenza Seasons

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.


Figure 2: Estimated U.S. Influenza Burden, By Season


Estimated US Influenza Burden, By Season

Supporting Research

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