Disease Burden of Flu

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Each year CDC estimates the burden of influenza in the U.S. CDC uses modeling to estimate the number of flu illnesses, medical visits, hospitalizations, and deaths related to flu that occurred in a given season. The methods used to calculate these estimates are described on CDC’s webpage, How CDC Estimates the Burden of Seasonal Flu in the U.S.

CDC uses the estimates of the burden of flu in the population and the impact of flu vaccination to inform policy and communications related to flu.

How CDC Estimates the Burden of Flu

Why CDC Estimates the Burden of Flu

Past Season Estimates

Frequently Asked Questions about Estimated Flu Burden

Preliminary In-Season Disease Burden Estimates

A person working on a digital chart and looking at data.

CDC provides weekly, preliminary estimates of the cumulative in-season numbers of flu illnesses, medical visits, hospitalizations, and deaths in the United States.

Flu Burden Averted from Vaccination

CDC estimates the burden of flu and the impact of annual flu vaccination in the U.S using a model that estimates the numbers of flu illnesses, medical visits and hospitalization prevented by vaccination.

Figure 1: Estimated Range of Annual Burden of Flu in the U.S. from 2010 – 2020

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The burden of flu 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 effects of flu varies, it places a substantial burden on the health of people in the United States each year.

CDC estimates that flu has resulted in 9 million – 41 million illnesses, 140,000 – 710,000 hospitalizations and 12,000 – 52,000 deaths annually between 2010 and 2020.

Table 1: Estimated Flu Disease Burden, by Season — United States, 2010-2011 through 2021-2022** Flu Seasons
	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)
2017-2018	41,000,000	(35,500,000 – 53,000,000)	21,000,000	(18,000,000 – 27,000,000)	710,000	(560,000 – 1,100,000)	52,000	(3,000 – 95,500)
2018-2019	29,000,000	(25,000,000 – 40,000,000)	17,000,000	(11,500,000 – 18,500,000)	380,000	(300,000 – 66,000)	28,000	(19,000 – 97,000)
2019-2020	36,000,000	(29,000,000 – 71,000,000)	16,000,000	(13,000,000 – 32,000,000)	390,000	(313,000 – 750,000)	25,000	(18,000 – 79,000)
Preliminary estimates*
2021-2022*	9,000,000	(7,700,000 – 15,000,000)	4,000,000	(3,600,000 – ,300,000)	100,000	(82,000 – 176,000)	5,000	(3,700 – 20,000)