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Influenza, or flu, is a viral infection of the nose, throat, bronchial tubes and lungs. There are 2 main types of virus: A and B. Each type includes many different strains which tend to change each year.

Influenza is highly contagious and is easily transmitted through contact with droplets from the nose and throat of an infected person who is coughing and sneezing.


Typical flu symptoms include headache, fever, chills, cough and body aches. Intestinal symptoms are uncommon. Although most people are ill for only a few days, some people have a much more serious illness, such as pneumonia, and may need to be hospitalized. Thousands of people die each year in the United States from the flu or related complications.

Prevention and Control

Coughs and sneezes should be covered or shielded to protect others. Wash your hands before touching your nose, mouth or eyes. Routine immunization against influenza is the most important control measure. Influenza vaccines may be available (flu shot) through your personal physician or local health department throughout the influenza season. When influenza type A occurs, amantadine and rimantadine may be prescribed for certain individuals to prevent influenza infection. A few studies have shown that the neuraminidase inhibitors are effective in preventing influenza, however, they are currently only licensed for the treatment of influenza. Because new influenza viruses often appear, the effectiveness of the vaccine sometimes varies from one year to the next. Nevertheless, studies have shown that even in years when new strains emerge, people in high-risk groups who obtain annual flu shots tend to have milder illness and are less likely to be hospitalized with complications due to influenza.

People who are allergic to egg protein or other vaccine components should not be vaccinated against influenza.


Mayo Clinic Influenza Overview