Disease Burden of Flu
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.
CDC provides weekly, preliminary estimates of the cumulative in-season numbers of flu illnesses, medical visits, hospitalizations, and deaths in the United States.
Figure 1: Estimated Range of Annual Burden of Flu in the U.S. from 2010 – 2020
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.
Figure 2: Estimated U.S. Flu Burden, By Season
* Estimates are not available for the due to minimal influenza activity.
- Q&A: Seasonal Flu-Associated Hospitalizations in the United States.
- Study: Annual estimates of the burden of seasonal flu in the United States: A tool for strengthening flu surveillance and preparedness. Flu Other Respir Viruses. 2018
- Study: Estimating flu disease burden from population-based surveillance data in the United States. PLoS One. 2015
- Study: The US Flu Hospitalization Surveillance Network. Emerg Infect Dis. 2015
- Study: Hospitalizations associated with flu and respiratory syncytial virus in the United States, 1993-2008. Clin Infect Dis. 2012
- Study: Flu-associated hospitalizations in the United States. JAMA. 2004
- Study: Estimates of global seasonal flu-associated respiratory mortality: a modelling study. Lancet. 2017
- Web article: Seasonal flu death estimate increases worldwide.
- Study: Global role and burden of flu in pediatric respiratory hospitalizations, 1982-2012: A systematic analysis. PLoS Med. 2016
- Web article: CDC Collaborative Study: Flu 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 Flu-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 flu—United States, 1976–2007. MMWR. 2010
- Study: Mortality associated with flu 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.
- Study: The annual impact of seasonal flu in the US: measuring disease burden and costs. Vaccine. 2007
- CDC Foundation: Flu Prevention Infographic, “Business Challenges”.