Estimated Influenza-Related Illnesses, Medical Visits, Hospitalizations, and Deaths in the United States — 2019–2020 Influenza Season

The burden estimates on this page have been updated from the preliminary estimates reported in October 2022, October 2021, and November 2020 based on the availability of additional data. Burden estimates for the 2019-2020 flu season are now considered final. More information on why preliminary flu burden estimates change is available below.

The overall burden of influenza (flu) for the 2019-2020 was an estimated 35 million flu-related illnesses, 16 million flu-related medical visits, 390,000 flu-related hospitalizations, and 25,000 flu-related deaths (Table 1).

For the past several years, CDC has estimated the numbers of flu-related illnesses, medical visits, hospitalizations, and deaths. More information on How CDC Estimates Flu Burden and Why CDC Estimates Flu Burden is available.3

Table 1: Estimated flu disease burden, by age group — United States, 2019-2020 flu season
Symptomatic Illnesses Medical Visits Hospitalizations Deaths
Age group Estimate 95% UI Estimate 95% UI Estimate 95% UI Estimate 95%UI
0-4 yrs 3,783,318 (2,784,324, 8,271,122) 2,534,823 (1,827,494, 5,529,562) 26,376 (19,411, 57,663) 367 (128, 1,568)
5-17 yrs 7,030,212 (4,889,043, 19,533,608) 3,655,710 (2,483,764, 10,022,293) 19,276 (13,405, 53,559) 163 (27, 669)
18-49 yrs 14,406,940 (9,420,406, 40,338,052) 5,330,568 (3,363,101, 14,825,249) 80,866 (52,877, 226,418) 2,492 (1,378, 8,913)
50-64 yrs 8,712,272 (6,086,659, 21,872,370) 3,746,277 (2,541,096, 9,251,388) 92,391 (64,547, 231,950) 6,200 (3,611, 22,359)
65+ yrs 1,903,130 (1,293,282, 4,603,468) 1,065,753 (704,953, 2,606,745) 173,012 (117,571, 418,497) 16,278 (9,846, 61,651)
All ages 35,835,872 (28,590,418, 70,051,903) 16,333,131 (13,117,497, 30,717,980) 391,921 (311,521, 725,364) 25,500 (18,053, 78,834)
Table 2: Estimated rates of flu-related disease outcomes, per 100,000, by age group — United States, 2019-2020 flu season
Illness rate Medical visit rate Hospitalization rate Mortality rate
Age group Estimate 95% UI Estimate 95% UI Estimate 95% UI Estimate 95% UI
0-4 yrs 19,325.60 (14,222.7, 42,249.9) 12,948.20 (9,335.1, 28,245.7) 134.7 (99.2, 294.5) 1.9 (0.7, 8.0)
5-17 yrs 13,149.80 ( 9,144.8, 36,537.0) 6,837.90 (4,645.8, 18,746.4) 36.1 (25.1, 100.2) 0.3 (0.0, 1.3)
18-49 yrs 10,423.50 ( 6,815.7, 29,184.7) 3,856.70 (2,433.2, 10,726.1) 58.5 (38.3, 163.8) 1.8 (1.0, 6.4)
50-64 yrs 13,845.30 ( 9,672.8, 34,759.0) 5,953.50 (4,038.2, 14,702.1) 146.8 (102.6, 368.6) 9.9 (5.7, 35.5)
65+ yrs 3,520.50 ( 2,392.4,  8,515.8) 1,971.50 (1,304.1,  4,822.1) 320 (217.5, 774.2) 30.1 (18.2, 114.0)

Uncertainty interval: Adjusted estimates are presented in two parts: an uncertainty interval [UI] and a point estimate. The uncertainty interval provides a range in which the true number or rate of flu illnesses, medical visits, hospitalizations, or deaths would be expected to fall if the same study was repeated many times, and it gives an idea of the precision of the point estimate. A 95% uncertainty interval means that if the study were repeated 100 times, then 95 out of 100 times the uncertainty interval would contain the true point estimate. Conversely, in only 5 times out of a 100 would the uncertainty interval not contain the true point estimate.

woman getting vacine

CDC estimates the flu-related illnesses, hospitalizations, and deaths prevented by seasonal flu vaccination.

Why did the estimates for the 2019-2020 flu season change compared with previous estimates for this season?

CDC’s model used to estimate the burden of flu includes information collected about flu testing practices. Because current testing data was not available at the time of estimation (it takes approximately two years to finalize information on flu testing practices), the estimates that were previously published on the CDC website were made using testing information from prior flu seasons.

Since then, complete information to estimate the burden of the 2019-2020 flu season has become available. Since testing for flu has increased over time, the adjustment for under-detection of flu was lower and the 2019-2020 burden estimates decreased.

In addition, the death estimates for the 2019-2020 season increased after incorporating information from this season. It is possible that the reason for the increase in the number of deaths is because more deaths were categorized as pneumonia and influenza deaths, despite removing time periods impacted by the emergence of COVID-19. Also, it is possible that the adjustment factors increased because testing for flu decreased during the 2019-2020 season especially as COVID-19 began to surge. Although we excluded data from April 2020 through the end of this season, it is possible that data during the first few months of 2020 could be affected by COVID-19 before it was recognized.

The 2019-2020 season estimates are now considered final. At this time, there are no plans to estimate the flu burden for the 2020-2021 season because there was very little flu activity across the United States.

More information on How CDC Estimates Flu Burden is available, as well as answers to frequently asked questions about CDC’s flu burden estimates.

Background and Results: 2019–2020 Burden Estimates

Flu activity in the United States during the 2019–2020 season began to increase in November and was consistently high through January and February.  The season was characterized by two consecutive waves of activity, beginning with influenza B viruses and followed by A(H1N1)pdm09 viruses. Overall, influenza A(H1N1)pdm09 viruses were the most commonly reported influenza viruses this season. Activity began to decline in March, perhaps associated with community prevention measures for COVID-19 (5-6). The 2019-20 season is described as having moderate severity; however, the effect of flu differed by age group and the severity of the season in some age groups was higher. Hospitalization rates among children 0-4 years old and adults 18-49 years old were higher than observed during the 2009 H1N1 pandemic (6).

CDC estimates that the burden of illness during the 2019–2020 season was moderate with an estimated 35 million people sick with flu, 16 million visits to a health care provider for flu, 390,000 hospitalizations for flu, and 25,000 flu deaths  (Table 1). The number of cases of flu-related illness, medically attended illnesses, hospitalizations, and deaths were lower than some more recent seasons and similar to other seasons where influenza A(H1N1)pdm09 viruses dominated (7, 8).

The 2019–2020 flu season was atypical in that it was severe for children aged 0-4 years where rates of infections, medically attended illnesses, hospitalizations, and deaths were higher than those observed during the 2017-2018 season, a recent season with high severity (7). The burden of flu and the rates of flu-related hospitalization are usually higher for the very young and the very old, and while this was observed during the 2019–2020 season, rates of hospitalization in adults aged 18-49 years were the highest seasonal rates seen since the 2017-2018 season (Table 2). These rates mean that an estimated 14 million cases of flu in younger adults (aged 18-49 years), which is the second highest number of infections for this age group since CDC began reporting flu burden estimates in the 2010-11 season.

CDC’s estimates of hospitalizations and mortality associated with the 2019–2020 flu season show the effects that flu virus infections can have on society. Nearly 45,000 hospitalizations occurred in children aged < 18 years and 80,000 hospitalizations among adults aged 18-49 years. Forty-four percent of hospitalizations occurred in older adults aged ≥65 years. Older adults also accounted for 64% of deaths, which is lower than recent previous seasons. These findings continue to highlight that older adults are particularly vulnerable to severe disease with flu virus infection. An estimated 8,500 deaths (34% of all deaths) occurred among working age adults (aged 18–64 years), an age group for which flu vaccine coverage is often low (9). This also underscores that flu viruses can affect individuals of any age and prevention measures such as vaccination are important to reducing the impact of the seasonal epidemics on the population and healthcare system.

Deaths in children with laboratory-confirmed flu virus infection have been a reportable disease in the United States since 2004; 199 deaths were reported for the 2019-20 season as of October 31, 2023. However, flu-related pediatric deaths are likely under-reported, as not all children whose death was related to a flu virus infection may have been tested for flu (10,11). Therefore, we used a mathematical model to estimate the total number of pediatric deaths based on hospitalization rates and the frequency of death in and out of the hospital using death certificates. We estimate that an additional 530 deaths associated with flu occurred during the 2019-2020 season among children aged <18 years.

Burden Estimates Limitations

These estimates are subject to some limitations.


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