Flu (seasonal influenza): Symptoms and treatment
Seasonal influenza, often referred to as the flu, is a contagious viral respiratory illness.
On this page
- Symptoms of the flu
- Complications of the flu
- If you become ill
- Diagnosing the flu
- Treating the flu
- Consider becoming a FluWatcher
Symptoms of the flu
Flu symptoms may vary from person to person. Some people get mildly ill. Others get very sick.
Flu symptoms generally appear 1 to 4 days after exposure to the virus. Symptoms usually include the sudden appearance of:
- fever
- cough
- muscle aches and pain
Other common symptoms may include:
- chills
- tiredness
- headache
- sore throat
- loss of appetite
- runny or stuffy nose
Some people (especially children) may also have:
- diarrhea
- nausea and vomiting
Other symptoms to watch for in children
As a parent, you know your child best. Talk to a health care provider right away if your child is:
- not waking up or interacting with others
- having difficulty breathing
- not drinking or eating as usual
- not wanting to play or be held (irritable)
Complications of the flu
Possible serious complications and outcomes of the flu include:
- worsening of chronic health conditions
- heart complications
- pneumonia and respiratory failure
- hospitalization
- death
If you become ill
If you become infected with the flu, you can spread the virus to others from 1 day before to until about 5 days after your first symptoms. You're most contagious in the first 3 days after the start of your symptoms. Children and people with weakened immune systems may be contagious for longer.
To help prevent spreading the flu, stay home and avoid close contact with others for at least the first 3 days while you're most infectious. It's best to wait up to 5 days or until you feel better overall before resuming close contact with others. It's especially important to protect those who have a higher chance of developing complications from the flu.
In addition to staying home and avoiding close contact, you can help protect others by:
- wearing a well-fitting respirator or mask, for example if you:
- need to be around others
- must enter a public setting or seek medical care
- cleaning your hands regularly
- covering your coughs and sneezes
Most people recover from the flu in 7 to 10 days.
If you're at higher risk of complications from the flu and you develop symptoms, contact a health care provider for advice.
Before you go to an in-person appointment, tell the health care provider about your symptoms over the phone and follow their instructions.
If you need immediate medical attention, call 9-1-1 and tell them your symptoms.
Learn more:
- Flu: Who is most at risk
- Flu: Spread, prevention and risks
- Respiratory infectious diseases: Reduce your risk
- Respiratory infectious diseases: Mask use for reducing the spread
Diagnosing the flu
It can be hard to tell the difference between symptoms of the flu and other respiratory illnesses like COVID-19.
Your health care provider may diagnose the flu based on your:
- symptoms
- laboratory tests (nose or throat swab)
Treating the flu
Flu symptoms can improve with:
- rest
- fluids, like water
- over-the-counter medication to reduce fever or aches
In some cases, a health care provider may prescribe specific medication against the flu (for example, antivirals), especially if you're:
- very sick with severe symptoms
- at higher risk for complications
Over-the-counter cough and flu medicine should not be given to children younger than 6 years old. It's only safe to do so if your health care provider advises it.
Consider becoming a FluWatcher
FluWatchers is a volunteer program that helps track the activity of common viruses like the flu, respiratory syncytial virus (RSV) and COVID-19 in Canada.
Once you sign up, you'll receive an email once a week asking if you had a cough or fever in the previous week. This serves as an early warning sign for respiratory illness activity, which helps public health officials respond to potential outbreaks.
It only takes about 15 seconds to complete through our secure portal and your answers are anonymous.