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What is influenza (the flu)?

What is Influenza (Flu): 

Flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs. It can cause mild to severe illness, and at times can lead to death. The best way to prevent flu is by getting a flu vaccine each year. 

Flu Symptoms:

Influenza (flu) can cause mild to severe illness, and at times can lead to death. Flu is different from a cold. Flu usually comes on suddenly. People who have flu often feel some or all of these symptoms:

  • fever* or feeling feverish/chills
  • cough
  • sore throat
  • runny or stuffy nose
  • muscle or body aches
  • headaches
  • fatigue (tiredness)
  • some people may have vomiting and diarrhea, though this is more common in children than adults.

*It’s important to note that not everyone with flu will have a fever.

How Flu Spreads

Most experts believe that flu viruses spread mainly by tiny droplets made when people with flu cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby. Less often, a person might get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose or possibly their eyes.

How Many People Get Sick with Flu Every Year?

A 2018 CDC study published in Clinical Infectious Diseasesexternal icon looked at the percentage of the U.S. population who were sickened by flu using two different methods and compared the findings. Both methods had similar findings, which suggested that on average, about 8% of the U.S. population gets sick from flu each season, with a range of between 3% and 11%, depending on the season.

Preventing the Flu

The single best way to prevent the flu, even in healthy people, is to get a flu vaccine each fall. However, you're not helpless when it comes to practicing certain good health habits that can prevent the flu:

  • Good health habits include avoiding close contact: If possible, avoid close contact with people who are sick. When you are sick, keep your distance from others to protect them from getting sick too.
  • Stay home when you are sick. If possible, stay home from work, school, and errands when you are sick. You will help prevent others from you catching your illness.
  • Cover your mouth and nose. If you can't stay home, cover your mouth and nose with a tissue when coughing or sneezing or catch your cough by coughing into your upper sleeve, not your hands. It may prevent those around you from getting sick.
  • Clean your hands. Washing your hands often will help protect you from germs. This measure may be the single best healthy habit that one can acquire.
  • Avoid touching your eyes, nose or mouth. Germs are often spread when a person touches something that is contaminated with germs and then touches his or her eyes, nose, or mouth.