Influenza (flu) is a contagious viral infection that can cause mild to severe symptoms and life-threatening complications, including death, even in healthy children and adults.
Influenza viruses spread mainly from one individual to another through coughing or sneezing. Less often, they can also spread through touching a contaminated surface and then touching the mouth, eyes, or nose. Individuals can pass flu on to others even before their own symptoms start and for a week or more after symptoms begin.
Burden
While the numbers vary, in the US, millions of individuals get sick, hundreds of thousands are hospitalized, and tens of thousands die from flu and related complications each year. Flu also affects employers and businesses and costs an estimated $11.2 billion in direct and indirect costs in the US annually. During the 2019-2020 flu season, flu vaccination prevented approximately 7.5 million flu illnesses, 105,000 hospitalizations, and 6,300 deaths.
Symptoms
Flu is not just a common cold. It usually comes on suddenly, and people with flu may have some or all of the following symptoms (think F.A.C.T.S.):
- Fever
- Aches (muscle, body, and headaches)
- Chills
- Tiredness (fatigue)
- Sudden onset
- Cough, runny or stuffy nose, and/or sore throat
- Vomiting and diarrhea (more common in children than adults)
Prevention
The best way to prevent flu is to receive an influenza vaccination every year. The Centers for Disease Control and Prevention (CDC) recommends that everyone age 6 months and older get vaccinated annually. Flu vaccination is especially important this year to help protect individuals and prevent additional strain on an already overburdened US healthcare system. The best time to get vaccinated is in the early fall, before influenza viruses begin spreading in your community. However, vaccination throughout the flu season is still beneficial.
Flu vaccines are updated annually to protect against the influenza viruses research indicates are most likely to circulate during the upcoming season. Flu vaccines can vary in how well they work, but even in cases when flu vaccination does not prevent infection completely, it can reduce the severity and duration of disease and prevent serious complications. For more than 50 years, hundreds of millions of individuals in the US have safely received seasonal flu vaccines.
Treatment
Annual flu vaccination is the best way to prevent flu. Antiviral drugs are not a substitute for annual flu vaccination; however, prescription antiviral medications serve as an additional line of defense. CDC recommends that all individuals who are hospitalized, severely ill, or at high risk for developing serious flu-related complications should be treated with antiviral drugs immediately if flu is suspected.
Treatment of flu with antiviral drugs can reduce influenza symptoms, shorten the duration of illness by one to two days, and prevent serious complications, like pneumonia. Antivirals work best when taken within 48 hours of getting sick, but may still be beneficial when given later in the course of illness.
Healthcare professionals may treat patients based on their clinical judgment and knowledge about the level of local flu activity. For additional information, see CDC Influenza Antiviral Medications: Summary for Clinicians.
Last Reviewed January 2022
Source: Centers for Disease Control and Prevention
Additional Resources
2021 Chronic Health Conditions Surveys: Gaps between Healthcare Professionals and Adult Patients
The National Foundation for Infectious Diseases (NFID) commissioned two national surveys (conducted online from October 28-November 8, 2021) to better understand knowledge, attitudes, and practices toward flu and pneumococcal disease vaccination as well as communication between healthcare professionals (HCPs) and adult patients with chronic health conditions.
Flu and COVID-19 Resources
The best way to help protect against flu and COVID-19 is to get vaccinated
Myths and Facts About Influenza (Flu)
Answers to common myths about influenza and flu vaccines
Are You at Risk for Serious Flu-Related Complications?
Influenza (flu) is not just a common cold. Anyone can get sick with flu, but certain people are at high risk of developing serious flu-related complications.
Influenza (Flu) Treatment
Certain antiviral drugs can help reduce symptoms of influenza (flu), shorten the duration of illness, and prevent complications
Take 3 Steps to Fight Flu
Take these three steps to help protect yourself and others from influenza (flu)
Flu Preparedness Guide
To help prepare for flu season, download the NFID Flu Preparedness Guide to learn more about best practices for treating and preventing the spread of flu, as well as tips on assembling a flu preparedness kit and emergency contact list
Infectious Disease Memes
Share these memes on social media to remind friends and family to #GetVaccinated and stay healthy this holiday season!
Flu Alert: The Impact of Flu on Adults 65+
23-second video public service announcement on the burden of influenza (flu) in adults age 65 years and older and the importance of getting vaccinated
More Flu Resources
Flu resources from A to Z from the National Foundation for Infectious Diseases (NFID) and partners
Healthcare Professionals and Influenza Vaccination
Sharable fact sheet outlining the benefits of influenza immunization for healthcare professionals
Myths and Facts About Flu and Children
Get the facts about flu and children
