by Amy Scholten, MPH
Influenza is a common infection that spreads easily. It is more often called the flu. The illness can range from mild to severe. It can be fatal in some. There are three types of flu: Type A, Type B, and less common Type C.
The flu is caused by a virus. There are many 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 past health. A physical exam may be done. Diagnosis is usually based on symptoms.
The doctor may take samples from the nose or throat for testing but it is rare.
Most can clear the virus on their own. Treatment can help to ease symptoms. The flu usually lasts 7 to 10 days. A cough or tiredness may last longer. 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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