Influenza (flu)

Influenza is a viral infection that attacks your respiratory system — your nose, throat and lungs. Influenza, commonly called the flu, is not the same as the stomach "flu" viruses that cause diarrhea and vomiting.

Influenza and its complications can be deadly. People at higher risk of developing flu complications include:

  • Young children
  • Adults older than 65
  • Pregnant women
  • People with weakened immune systems
  • People who have chronic illnesses

Your best defense against influenza is to receive an annual vaccination.

Symptoms Causes Risk factors Complications Prevention

Initially, the flu may seem like a common cold with a runny nose, sneezing and sore throat. But colds usually develop slowly, whereas the flu tends to come on suddenly. And although a cold can be a nuisance, you usually feel much worse with the flu.

Common signs and symptoms of the flu include:

  • Fever over 100 F (38 C)
  • Aching muscles, especially in your back, arms and legs
  • Chills and sweats
  • Headache
  • Dry cough
  • Fatigue and weakness
  • Nasal congestion

When to see a doctor

Most people who get the flu can treat themselves at home and often don't need to see a doctor.

If you have flu symptoms and are at risk of complications, see your doctor right away. Taking antiviral drugs within the first 48 hours after you first notice symptoms may reduce the length of your illness and help prevent more-serious problems.

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