Flu Symptoms, Causes, and Risk Factors

We all are at risk for getting and spreading the flu. Having the flu may keep you home from work or school, not to mention making you feel pretty miserable for a week or two. If you have asthma or other lung diseases, you are at higher risk of developing complications from the flu.

What Are the Symptoms of Influenza?

Flu symptoms often appear suddenly. People at higher risk of complications, such as those with chronic lung disease, should seek prompt medical attention. Treatment may include antiviral medicine which can reduce symptoms if started within a day or two of getting sick.

Symptoms of influenza can include:

  • Sudden onset of high fever
  • Headache, muscle aches and joint pain
  • Cough (usually dry)
  • Chills
  • Sore throat
  • Nasal congestion and runny nose
  • Fatigue
  • Stomach symptoms such as nausea, vomiting or diarrhea may occur but are more common in children than adults.

Most people recover from the flu within one or two weeks, but others, especially the elderly, may feel weak for a long time even after other symptoms go away.

Flu symptoms in children

Flu symptoms in school-age children and adolescents are similar to those in adults. Children tend to have higher temperatures than adults, ranging from 103°F to 105°F. Flu in preschool children and infants is hard to pinpoint since its symptoms are so similar to infections caused by other viruses.

If the symptoms mentioned above are present and the flu is circulating in your area, please contact a healthcare provider immediately.

What Causes the Flu?

The flu is caused by influenza viruses that infect the nose, throat, and lungs. These viruses spread when people with flu cough, sneeze or talk, sending droplets with the virus into the air and potentially into the mouths or noses of people who are nearby. You can also get flu by touching a surface or object that has flu virus on it and then touching your own mouth, eyes or nose.

You can spread the flu before you know you are sick, beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick. Some people, especially young children and people with weakened immune systems, might be able to infect others for an even longer time.

Flu Risk Factors

Influenza is a very serious illness for anyone at high risk. Certain diseases that place people at high risk include:

  • chronic lung diseases such as asthma, COPD, bronchiectasis, or cystic fibrosis
  • heart disease
  • chronic kidney disease
  • diabetes or other chronic metabolic disorder
  • morbid obesity
  • severe anemia (including sickle cell anemia)
  • diseases (HIV, AIDS) or treatments (steroids, chemotherapy) that suppress immunity
  • liver disorders
  • children and adolescents who are receiving long-term aspirin therapy

4 Ways to Reduce Your Flu Risk

1. Get a flu shot 2. Wash your hands 3. Get prompt medical attention if you develop flu symptoms 4. Keep your distance when you're sick or if you're around someone who is sick.

When to See Your Doctor

For your yearly flu shot. Everyone 6 months and older should visit a healthcare provider every year to get a flu vaccine. The best time to go is soon after the vaccine becomes available in the fall.

If you develop flu symptoms. If you do get sick, it is important for you to call your doctor as soon as possible to receive prompt treatment with antivirals—especially if you are at high risk for complications. Antivirals can be effective in reducing the severity of flu and the duration of the disease.

For flu complications. Pneumonia can be caused by the flu virus or by bacteria that get into the lungs when the body's defense system is weakened by the flu. See a doctor if you:

  • Have difficulty breathing;
  • Experience chest pain as a result of coughing; or
  • Are coughing up yellow, green or bloody phlegm.

Other infections that may be associated with the flu include sinusitis, bronchitis and ear infections.

If your cough won't go away. You may have a cough that lasts for weeks to months after flu symptoms go away; and it may keep you up at night. This cough has been associated with asthma-like symptoms, and can be treated with asthma medications. Consult a healthcare provider if you have this kind of cough.

Reviewed and approved by the American Lung Association Scientific and Medical Editorial Review Panel.

Page last updated: November 17, 2022

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