Symptoms of flu (influenza)

Learn about the symptoms of flu, what to look for and what to do if you become ill.

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What are the symptoms of flu?

Some people get mildly ill, while others get very sick.

Flu symptoms usually include the sudden appearance of:

  • high fever (39°C and above)
  • cough
  • muscle aches

Other common symptoms include:

  • headache
  • chills
  • loss of appetite
  • fatigue (tiredness)
  • sore throat
  • runny or stuffy nose

Some people, especially children, may also experience:

  • a stomach ache
  • diarrhea
  • nausea and vomiting

It takes 1 to 4 days for flu symptoms to appear after exposure to the virus.

Most people recover from the flu in 7 to 10 days. Others may develop serious complications, such as pneumonia (a lung infection), and may need hospital care.

Differences between the flu and a cold

A cold infects just your nose and throat, while the flu also affects your lungs.

Cold symptoms are unpleasant but are usually milder than the flu. They include:

  • runny nose
  • sneezing
  • cough
  • sore throat

Read more about how to tell if you have a cold or the flu.

What do you do if you become ill?

If you are mildly ill, stay home and avoid contact with other people until your symptoms are gone. This will help prevent the spread of the virus.

If you are a person at high risk of flu-related complications, contact your health care provider. Tell them about your symptoms.

See a health care provider immediately if you develop any of these symptoms:

  • shortness of breath
  • fast or trouble breathing
  • pain in your chest
  • blueish or grey skin colour
  • bloody or coloured mucous in your mouth or spit
  • sudden dizziness or confusion
  • severe or ongoing vomiting
  • a high fever (39°C and above) that lasts more than 3 days
  • low blood pressure

Tell your health care provider about your flu symptoms over the phone before your appointment. That way, they can arrange to see you without exposing other people to the virus.

Also see a health care provider if you are caring for a child who is sick with the flu and is:

  • not drinking or eating as usual
  • not waking up or interacting with others
  • irritable (not wanting to play or be held)
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