by Amy Scholten, MPH
Influenza (also called the flu) is a viral infection. It affects the respiratory system. It can be mild to severe. In certain people it can be fatal.
There are three types:
The flu is caused by a virus. There are different strains of flu virus. The strains often change from year to year.
The flu virus may be spread by:
Things that raise the risk of getting the flu are:
Some people have a higher risk for severe flu, or problems from the flu. This includes children less than 5 years old and adults over 50 years old. Other things that raise the risk are:
Symptoms usually start quickly. They may be:
The doctor will ask about your symptoms and health history. A physical exam may be done. Diagnosis is usually based on symptoms.
The doctor may take samples from the nose or throat for testing. This can confirm the diagnosis.
The flu usually lasts 7 to 10 days. A cough or tiredness may last longer. The goal is to ease symptoms and prevent problems.
People with severe symptoms or problems may be treated in the hospital.
Treatment options are:
To reduce the risk of getting the flu:
Antiviral medicines may be advised for certain people.
Centers for Disease Control and Prevention
World Health Organization
Public Health Agency of Canada
The College of Family Physicians of Canada
Gaitonde DY, Moore FC, et al. Influenza: diagnosis and treatment. Am Fam Physician. 2019;100(12):751-758.
Inactivated influenza VIS. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/vaccines/hcp/vis/vis-statements/flu.html. Accessed January 29, 2021.
Influenza. American Lung Association website. Available at:
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Accessed January 29, 2021.
Influenza in adults. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/influenza-in-adults. Accessed January 29, 2021.
Influenza in children. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/influenza-in-children . Accessed January 29, 2021.
Key facts about seasonal influenza (flu). Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/flu/keyfacts.htm. Accessed January 29, 2021.
Seasonal influenza vaccination. EBSCO DynaMed website. Available at: https://www.dynamed.com/prevention/seasonal-influenza-vaccination. Accessed on February 24, 2021.
What you should know about flu antiviral drugs. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/flu/antivirals/whatyoushould.htm. Accessed January 29, 2021.
Last reviewed January 2021 by EBSCO Medical Review Board Mary Beth Seymour, RN
Last Updated: 2/24/2021
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