Symptoms of flu

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.

Flu symptoms may vary from person to person. Some people get mildly ill. Others get very sick. Most healthy people will not need medical treatment for flu. 

Symptoms of influenza can include:

• Sudden onset of high fever
• Headache, muscle aches and joint pain
• Cough (usually dry)
• Sore throat
• Nasal congestion and runny nose
• Muscle/body aches and chills
• 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 older adults, may feel weak for a long time even after other symptoms go away.

Possible 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. 

It is possible to develop other serious complications from flu, such as:

• worsening of chronic health conditions
• heart complications
• respiratory failure
• hospitalization
• death

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

See a doctor if you:

• Have difficulty breathing;
• Have persistent chest or abdomen pain or pressure; or
• Are coughing up yellow, green or bloody phlegm.
• Experience worsening of your chronic medical condition(s)

Diagnosing flu

It can be hard to tell the difference between symptoms of the flu and other respiratory illnesses, especially in young children. 

If a healthcare provider suspects you or your child my have flu, they can test for it by taking a swab of your throat or inside your nose. This swab will be tested by a laboratory. Your provider will also consider the symptoms that you or your child are experiencing. You may receive the results on the same day, or it may take a few days, depending on the type of testing.

Treating flu

Most of the time, people can take care of the flu at home. 

• Stay home and rest. Get lots of sleep.
• Stay away from other people and avoid spreading your germs. Wash your hands, clean common areas and take these other steps to avoid spreading your germs.
• Drink lots of fluids to prevent dehydration. Drink clear fluids such as water, broth or sports drinks.
• For your headache, muscles aches and fever, you can take over-the-counter medicines like acetaminophen or ibuprofen. Children and teens should not take aspirin (ASA or acetylsalicylic acid). If you’re not sure what to take, call a pharmacist.

If you have asthma or COPD

If you have asthma or COPD, it’s important that you follow the directions in your Action Plan. You may have to take extra medicine to control your symptoms. Call your healthcare provider if your symptoms don’t improve after a few days. 

Watch for warning signs of severe flu. If it’s hard to breathe or your rescue medicine isn’t working, call 911 or your local emergency number.

Antiviral medication

Flu antiviral drugs can reduce the severity of flu symptoms by blocking the exit of the influenza virus from respiratory cells, preventing further replication of the virus. 

Not everyone with flu will be given antivirals. Your healthcare provider will consider your symptoms and when they began, the severity of illness and if you have any risk factors for complications. Individuals with severe symptoms, at risk of developing severe symptoms or at risk of transmitting the virus to someone at high risk for severe symptoms are typically given priority to receive antivirals.

You do not have to wait for a positive test to begin taking this medication. This medication must be started as soon as possible to be effective (within 48 hours of symptom onset).

Preventing flu

Get the flu shot every year. 

The flu shot is your best defense against the flu. It’s recommended for most people over six months old, and especially recommended for people in high-risk groups:

• Seniors
• Children
• Childcare workers
• Healthcare workers
• People with weak immune systems
• People with chronic (long-term) diseases like asthma and COPD
• Pregnant women

You can read more about vaccinations to prevent common respiratory infections.

Stay home if you’re sick

You can spread the flu virus to others from one day before to about five days after your first symptoms. You’re most contagious in the first three days after the start of your symptoms. Children and people with weakened immune systems may be contagious for longer.

Wash or sanitize your hands

Use alcohol-based hand sanitizer or wash your hands thoroughly with soap and water several times a day. This will help keep germs at bay and help you avoid most of the common infectious diseases that are spread by hand. 

Cover your coughs

To help stop the spread of germs, cover your mouth and nose with a tissue or cough or sneeze into your elbow. Stay away from crowds during peak cold and flu season, get plenty of rest, eat well and keep your stress levels under control.

Wear a mask

Wearing a mask to keep from getting sick or getting others sick has become more common in Canada following the COVID-19 pandemic. Wearing a mask can protect against cold, flu or COVID-19 viruses that can be spread by respiratory droplets (sneezing, coughing, etc.).

Canadian workers may be exposed to an excessive amount of dust, fumes, smoke, gases, vapors or mists in the workplace. Poor ventilation, closed-in working areas and heat increase are also disease-causing culprits. Avoid breathing in toxic fumes from chemicals, solvents or paints. Wear protective masks (N95 or better) when you work with chemicals and report unsafe working conditions. Take advantage of lung screening and other health programs offered at work.

Stay away from sick people

If you have a long-term lung disease like asthma or COPD, you are more likely to get a respiratory infection like a cold, the flu or COVID-19. This could make your COPD or asthma symptoms much worse. It’s best to stay away from people who are sick.

Flu in children

Flu can be dangerous for children. Infants and young children, unvaccinated children and children with certain underlying medical conditions are most at risk of serious flu complications or even death 

Complications from flu among young children can include pneumonia, dehydration, worsening of chronic conditions like asthma, brain dysfunction, sinus problems and ear infections. 

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)