Influenza, also called the flu, is one of the most infectious diseases worldwide. Its symptoms range from mild to severe, and include sore throat, cough, runny nose, fever, headache, and muscle pain, but can also cause severe illness and death among high-risk populations such as the elderly and children. During the 2023-2024 flu season, there were 40 million cases of influenza in the United States. Influenza deaths Although influenza does not require medical attention for most people, it can be deadly, and causes thousands of deaths every year. The impact of influenza varies from year to year. The number of influenza deaths during the 2023-2024 flu season was 27,965. The vast majority of deaths attributed to influenza during the 2023-2024 flu season occurred among those aged 65 years and older. Vaccination An annual influenza vaccination remains the most effective way of preventing influenza. During the 2022-2023 flu season, influenza vaccinations prevented an estimated 2,479 deaths among U.S. adults aged 65 years and older. Although, flu vaccinations are accessible and cheap, a large share of the United States population still fails to get vaccinated every year. In 2022-2023, only 35 percent of those aged 18 to 49 years received a flu vaccination, much lower compared to children and the elderly.

The burden of influenza in the United States can vary from year to year depending on which viruses are circulating, how many people receive an influenza vaccination, and how effective the vaccination is in that particular year. During the 2023-2024 flu season, around 28,000 people lost their lives to the disease. Although most people recover from influenza without needing medical care, the disease can be deadly among young children, the elderly, and those with weakened immune systems or chronic illnesses. Deaths due to influenza Even though most people recover from influenza without medical care, influenza and pneumonia can be deadly, especially for older people and those with certain preexisting conditions. Influenza is a common cause of pneumonia and although most cases of influenza do not develop into pneumonia, those that do are often more severe and more deadly. Deaths due to influenza are most common among the elderly, with a mortality rate of around 32 per 100,000 population during the 2023-2024 flu season. In comparison, the mortality rate for those aged 50 to 64 years was 9.1 per 100,000 population. Flu vaccinations The most effective way to prevent influenza is to receive an annual influenza vaccination. These vaccines have proven to be safe and are usually cheap and easily accessible. Nevertheless, every year a large share of the population in the United States still fails to get vaccinated against influenza. For example, in the 2022-2023 flu season, only 35 percent of those aged 18 to 49 years received a flu vaccination. Unsurprisingly, children and the elderly are the most likely to get vaccinated. It is estimated that during the 2022-2023 flu season, vaccinations prevented over 929 thousand influenza cases among children aged 6 months to 4 years.

During the 2023-2024 flu season in the United States, an estimated 27,965 people died from influenza. The vast majority of deaths due to influenza occur among the elderly, with those aged 65 years and older accounting for 19,038 deaths during the 2023-2024 flu season. During this time, the mortality rate from influenza among those aged 65 years and older was around 32 per 100,000 population, compared to a mortality rate of two per 100,000 population among those aged 18 to 49 years. Influenza deaths Although most people recover from influenza without the need of medical care, influenza and pneumonia are still major causes of death in the United States. Influenza is a common cause of pneumonia and cases in which influenza develops into pneumonia tend to be more severe and more deadly. However, the impact of influenza varies from year to year depending on which viruses are circulating. For example, during the 2017-2018 flu season around 52,000 people died due to influenza, whereas in 2023-2024 total deaths amounted to 28,000. Preventing death The most effective way to prevent influenza is to receive an annual influenza vaccination. These vaccines have proven to be safe and are usually cheap and easily accessible. Each year, flu vaccinations prevent thousands of influenza cases, hospitalizations and deaths. It was estimated that during the 2022-2023 flu season, vaccinations prevented the deaths of around 2,479 people aged 65 years and older.

Cumulative case counts for influenza and Respiratory Syncytial Virus (RSV) by county. Updates every Tuesday. Data contains cases reported from September 28, 2025 through the previous Saturday.

The Seasonal Influenza dataset provides information on influenza cases during specific seasons across various regions in the United States. It includes data on the number of positive flu cases, the total specimens tested, and the percentage of positive results for different types of respiratory viruses (e.g., Influenza A, Influenza B, and RSV). The dataset spans multiple years, capturing weekly flu activity. It contains numerical features such as Number_Positive, Specimens_Tested, and Percent_Positive, as well as categorical features like season, region, and Respiratory_Virus. This dataset is valuable for analyzing seasonal flu trends and regional outbreaks.

This dataset includes weekly counts of laboratory-confirmed influenza (flu) cases, by county and influenza type, going back to the 2009-10 season. The primary goal of this dataset is to provide users timely information about local influenza activity throughout the current influenza season. Although each influenza season is unique, historical data is also provided for trend comparison.

Cases are included that meet the New York State Department of Health’s (NYSDOH) standardized case definition, i.e., a positive result on any of the following influenza laboratory tests: • Rapid Influenza Diagnostic Tests (RIDT) • Immunofluorescence assays (DFA and IFA) • Rapid Molecular Assays • Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) • Other Nucleic Acid Amplification tests • Viral Culture

Please see the overview document for more details about NYSDOH’s influenza case definition. Cases reported during the CDC-defined influenza surveillance season (week 40-week 20 of the next calendar year; October through mid-May) are included. For more information see: http://www.health.ny.gov/diseases/communicable/influenza/surveillance/

In the United States, the highest rate of hospitalizations due to influenza are among those aged 65 years and older. During the 2023-2024 flu season, the rate of hospitalizations due to influenza among this age group was about 401 per 100,000 population, compared to a rate of around 47 per 100,000 for those aged 5 to 17 years. Influenza is a common viral infection that usually does not require medical treatment. However, for the very young, the old, and those with certain pre-existing conditions, influenza can be serious and even deadly. The burden of influenza in the United States The impact of influenza in the United States varies from year to year depending on the strain that is most prevalent during that season and the immunity in the population. Preliminary estimates show that around 28,000 people died from influenza during the 2023-2024 flu season. However, during the 2017-2018 flu season, an estimated 52,000 people lost their lives to influenza. The importance of flu vaccines The best way to avoid catching the flu and to reduce the virus’s overall burden on society is by receiving an annual flu vaccination. The CDC currently recommends that everyone over 6 months of age should get a flu vaccination every year, preferably by the end of October. The flu vaccine is safe, efficient, and reduces the number of illnesses, hospitalizations, and deaths caused by the virus. For example, during the 2022-2023 flu season, it was estimated that vaccinations averted almost 65 thousand influenza-related hospitalizations. However, despite the proven benefits and wide availability of flu vaccinations, a large percentage of people in the United States fail to receive a vaccination every year. During the 2022-2023 flu season, only about 35 percent of those aged 18 to 49 years were vaccinated against influenza, compared to 70 percent of those aged 65 years and older.

The CDC estimated an illness rate of around 15,686 per 100,000 for U.S. children aged 0 to 4 years for influenza during the 2023-2024 flu season. This statistic shows the estimated rate of influenza cases in the U.S. during the 2023-2024 influenza season, by age group.

This dataset contains the weekly estimated influenza risk level for each ZIP Code in Chicago. Estimates are made during flu season, which goes from MMWR week 40 to week 20 of the following year. The risk level is based on observed level of Influenza-Like Illness (ILI). ILI Activity Level is determined as follows: ILI percentage for each ZIP Code for the week is compared to the mean ILI percentage during the non-influenza months (summer months). Level 1 corresponds to an ILI percentage below the mean, level 2 to an ILI percentage less than one standard deviation (SD) above the mean, level 3 to an ILI percentage more than one, but less than two SDs above mean, and so on, with level 10 corresponding to an ILI percentage more than eight SDs above the mean. For more information on ESSENCE, which compiles the estimates, see https://www.dph.illinois.gov/data-statistics/syndromic-surveillance All data are provisional and subject to change. Information is updated as additional details are received. At any given time, this dataset reflects data currently known to CDPH. Numbers in this dataset may differ from other public sources.

Context

In light of COVID-19, I initially wanted to look into past flu events to see if there was any relationship.

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I found there were peak cases of influenza in the US leading up to COVID-19. There are many questions that had arisen due to this, but ultimately, I sought to figure out causal events of the higher and higher influenza cases. So, I examined the 2017-2018 flu season since it has the second-largest peak. I happened to remember the relatively large wildfire season that year, so I wondered if it could have caused an increase in flu incidence. Long story short, I utilized a difference in difference experiment and found out that wildfires did not cause a peak in flu incidence. Now, I hope this data would be of use to someone else.

Content

See file description.

Acknowledgements

We wouldn't be here without the help of others. If you owe any attributions or thanks, include them here along with any citations of past research.

Inspiration

As I mentioned earlier, there is more to be discovered, here. I have still yet to find out whether there is a relation between these past flu seasons and COVID-19. Or is this just a separate event?

The data for this competition comes from the National 2009 H1N1 Flu Survey (NHFS).

In their own words:

The National 2009 H1N1 Flu Survey (NHFS) was sponsored by the National Center for Immunization and Respiratory Diseases (NCIRD) and conducted jointly by NCIRD and the National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention (CDC). The NHFS was a list-assisted random-digit-dialing telephone survey of households, designed to monitor influenza immunization coverage in the 2009-10 season.

The target population for the NHFS was all persons 6 months or older living in the United States at the time of the interview. Data from the NHFS were used to produce timely estimates of vaccination coverage rates for both the monovalent pH1N1 and trivalent seasonal influenza vaccines.

National 2009 H1N1 Flu Survey Public-Use Data File Readme

The NHFS was conducted between October 2009 and June 2010. It was one-time survey designed specifically to monitor vaccination during the 2009-2010 flu season in response to the 2009 H1N1 pandemic. The CDC has other ongoing programs for annual phone surveys that continue to monitor seasonal flu vaccination.

Data use restrictions

The source dataset comes with the following data use restrictions:

The Public Health Service Act (Section 308(d)) provides that the data collected by the National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention (CDC), may be used only for the purpose of health statistical reporting and analysis.

Any effort to determine the identity of any reported case is prohibited by this law.

NCHS does all it can to ensure that the identity of data subjects cannot be disclosed. All direct identifiers, as well as any characteristics that might lead to identification, are omitted from the data files. Any intentional identification or disclosure of a person or establishment violates the assurances of confidentiality given to the providers of the information.

Therefore, users will:

1. Use the data in these data files for statistical reporting and analysis only.
2. Make no use of the identity of any person or establishment discovered inadvertently and advise the Director, NCHS, of any such discovery (1 (800) 232-4636).
3. Not link these data files with individually identifiable data from other NCHS or non-NCHS data files.

By using these data, you signify your agreement to comply with the above requirements.

National 2009 H1N1 Flu Survey Public-Use Data File Readme

Additional resources

• U.S. National 2009 H1N1 Flu Survey (NHFS)
• U.S. National Immunization Surveys (NIS)
• 2009 H1N1 Pandemic (H1N1pdm09 virus), by the U.S. CDC
• About Flu, by the U.S. CDC
• Key Facts About Seasonal Flu Vaccine, by the U.S. CDC

Data is provided courtesy of the United States National Center for Health Statistics.

U.S. Department of Health and Human Services (DHHS). National Center for Health Statistics. The National 2009 H1N1 Flu Survey. Hyattsville, MD: Centers for Disease Control and Prevention, 2012.

Images courtesy of the U.S. Navy and the Fort Meade Public Affairs Office via Flickr under the CC BY 2.0 license.

The data for this competition comes from the National 2009 H1N1 Flu Survey (NHFS).

In their own words:

The National 2009 H1N1 Flu Survey (NHFS) was sponsored by the National Center for Immunization and Respiratory Diseases (NCIRD) and conducted jointly by NCIRD and the National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention (CDC). The NHFS was a list-assisted random-digit-dialing telephone survey of households, designed to monitor influenza immunization coverage in the 2009-10 season.

The target population for the NHFS was all persons 6 months or older living in the United States at the time of the interview. Data from the NHFS were used to produce timely estimates of vaccination coverage rates for both the monovalent pH1N1 and trivalent seasonal influenza vaccines.

[National 2009 H1N1 Flu Survey Public-Use Data File Readme](ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Dataset...

This statistic displays the incidence of influenza cases that ended in hospitalization in Ireland during the 2018/19 flu season, by age. In this period, for those aged 65 years and over, approximately *** people per 100,000 in that age group were admitted to hospital as a result of influenza.

Influenza vaccination is the primary approach to prevent influenza annually. WHO/CDC recommendations prioritize vaccinations mainly on the basis of age and co-morbidities, but have never considered influenza infection history of individuals for vaccination targeting. We evaluated such influenza vaccination policies through small-world contact networks simulations. Further, to verify our findings we analyzed, independently, large-scale empirical data of influenza diagnosis from the two largest Health Maintenance Organizations in Israel, together covering more than 74% of the Israeli population. These longitudinal individual-level data include about nine million cases of influenza diagnosed over a decade. Through contact network epidemiology simulations, we found that individuals previously infected with influenza have a disproportionate probability of being highly connected within networks and transmitting to others. Therefore, we showed that prioritizing those previously infected for vaccination would be more effective than a random vaccination policy in reducing infection. The effectiveness of such a policy is robust over a range of epidemiological assumptions, including cross-reactivity between influenza strains conferring partial protection as high as 55%. Empirically, our analysis of the medical records confirms that in every age group, case definition for influenza, clinical diagnosis, and year tested, patients infected in the year prior had a substantially higher risk of becoming infected in the subsequent year. Accordingly, considering individual infection history in targeting and promoting influenza vaccination is predicted to be a highly effective supplement to the current policy. Our approach can also be generalized for other infectious disease, computer viruses, or ecological networks.

Given substantial regional differences in absolute humidity across the US and our understanding of the relationship between absolute humidity and influenza, we may expect important differences in regional seasonal influenza activity. Here, we assessed cross-seasonal influenza activity by comparing counts of positive influenza A and B rapid test results during the influenza season versus summer baseline periods for the 2016/2017 and 2017/2018 influenza years. Our analysis indicates significant regional patterns in cross-seasonal influenza activity, with relatively fewer influenza cases during the influenza season compared to summertime baseline periods in humid areas of the US, particularly in Florida and Hawaii. The cross-seasonal ratios vary from year-to-year and influenza type, but the geographic patterning of the ratios is relatively consistent. Mixed-effects regression models indicated absolute humidity during the influenza season was the strongest predictor of cross-seasonal influenza activity, suggesting a relationship between absolute humidity and cross-seasonal influenza activity. There was also evidence that absolute humidity during the summer plays a role, as well. This analysis suggests that spatial variation in seasonal absolute humidity levels may generate important regional differences in seasonal influenza activity and dynamics in the US.

This dataset contains the following files for California influenza surveillance data: 1) Outpatient Influenza-like Illness Surveillance Data by Region and Influenza Season from volunteer sentinel providers; 2) Clinical Sentinel Laboratory Influenza and Other Respiratory Virus Surveillance Data by Region and Influenza Season from volunteer sentinel laboratories; and 3) Public Health Laboratory Influenza Respiratory Virus Surveillance Data by Region and Influenza Season from California public health laboratories. The Immunization Branch at the California Department of Public Health (CDPH) collects, compiles and analyzes information on influenza activity year-round in California and produces a weekly influenza surveillance report during October through May. The California influenza surveillance system is a collaborative effort between CDPH and its many partners at local health departments, public health and clinical laboratories, vital statistics offices, healthcare providers, clinics, emergency departments, and the Centers for Disease Control and Prevention (CDC). California data are also included in the CDC weekly influenza surveillance report, FluView, and help contribute to the national picture of Influenza activity in the United States. The information collected allows CDPH and CDC to: 1) find out when and where influenza activity is occurring; 2) track influenza-related illness; 3) determine what influenza viruses are circulating; 4) detect changes in influenza viruses; and 5) measure the impact influenza is having on hospitalizations and deaths.