Disease Burden of Influenza

Estimates of Influenza Disease Burden

CDC calculates estimates of disease burden in the United States using surveillance data and modeling to adjust for sources of under-detection.

Flu Illness

Each year CDC estimates the number of people who become sick with flu illness in the U.S.

Flu-Associated Hospitalizations

The estimated number of Influenza hospitalizations has always varied from season to season.

Flu-Associated Deaths

Seasonal flu-related deaths occur in people for whom seasonal flu infection likely contributed to the cause of death.

Estimated Burden of Flu in the U.S. since 2010

The severity 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 9.2 million and 35.6 million illnesses, between 140,000 and 710,000 hospitalizations and between 12,000 and 56,000 deaths annually since 2010.

This image shows a pyramid with the range of flu cases, hospitalizations and deaths estimated annually in the United States since 2010. At the bottom of the pyramid is the numbers of flu cases, which is greatest (between 9.2 million and 60.8 million illnesses), followed by hospitalizations (between 140,000 and 710,000 hospitalizations), followed by deaths (between 12,000 and 56,000 deaths).

CDC tracks severity principally through its national Influenza Surveillance System that monitors key indicators like the percentage of deaths resulting from pneumonia or influenza, rates of influenza-associated hospitalizations, pediatric deaths and the percentage of visits to outpatient clinics for influenza-like illness. CDC then applies a statistical methodology to those data to classify severity as being low, moderate, high or very high. CDC also uses mathematical models to fill in the pyramid of the disease burden (see figure below) and estimate the impact of influenza immunization programs. Models are used to augment surveillance data because most of the surveillance systems only look at portions of the U.S. population and in some instances there can be significant under-reporting of influenza deaths and hospitalizations. This page includes links to key resources on the burden of influenza.

Estimated Influenza Disease Burden, by Season — United States, 2010-11 through 2016-17 Influenza Seasons

**Table 2:** Estimated Influenza Disease Burden, by Season — United States, 2010-11 through 2016-17 Influenza Seasons
Season	Estimated illnesses		Estimated medical visits		Estimated hospitalizations
Season	No.	95% CI	No.	95% CI	Hosp. rate (per 100,000)	No.	95% CI
2010-2011	21,100,000	17,600,000-27,700,000	10,000,000	8,190,000-13,200,000	91.2	282,000	239,000-374,000
2011-2012	9,230,000	7,280,000-13,800,000	4,300,000	3,390,000-6,450,000	44.8	139,000	116,000-206,000
2012-2013	35,600,000	30,100,000-44,300,000	16,600,000	14,000,000-20,800,000	188.8	593,000	510,000-733,000
2013-2014	28,400,000	25,000,000-33,000,000	12,600,000	10,900,000-14,800,000	101.9	322,000	283,000-377,000
2014-2015	34,300,000	30,300,000-40,100,000	16,200,000	14,100,000-19,200,000	221.8	707,000	624,000-839,000
Approximate 5-season range (No.)	9,230,000-35,600,000		4,300,000-16,600,000		139,000-707,000
2015-2016	24,600,000	21,500,000-28,600,000	11,100,000	9,570,000-13,100,000	95.9	308,000	271,000-362,000
2016-2017	30,900,000	27,300,000-35,900,000	14,500,000	12,500,000-17,100,000	185.6	600,000	525,000-709,000

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 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 Estimated Influenza Illnesses, Medical visits, and Hospitalizations 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 States. JAMA. 2003

Visit Estimated Influenza Illnesses, Medical visits, and Hospitalizations 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 costs. Vaccine. 2007
CDC Foundation: Flu Prevention Infographic, “Business Challenges”.

More Information

Infographics

The Benefits of Flu Vaccination 2016-2017 Infographic

Printer file (8.5″ x 11″) [613 KB, 1 page, Print Only]
Full Sized Infographic and Text Version

Business Pulse, how CDC protects the health of your business. Vaccination if the single best way to prevent flu. An estimated 45 percent of the U.S. population got vaccinated during 2012-2013.

CDC Foundation Business Pulse: Flu Prevention

Top of Page