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Influenza, also known as the flu, is a virus that spreads easily and can infect the nose, throat, and lungs. It is caused by influenza A and B viruses. Each year in Canada about five to 10 per cent of adults and 20 to 30 per cent of children are infected with influenza, usually in the late fall and winter.
Getting the flu vaccine each year is the best way to prevent the flu.
Like other respiratory viruses, flu is typically spread through respiratory droplets when people who are sick with the virus cough, sneeze, or talk near people who are within two meters. It has also been found that some respiratory viruses, including flu, can spread through very small droplets called aerosols, which can hang in the air for longer periods of time. Less commonly, a person may also get flu when they touch a surface or object that has the virus on it and then touch their own mouth, nose, or eyes.
It can take from one to four days to develop flu illness after being infected with the virus. People with flu may infect others beginning from one day before symptoms start until about five days after becoming sick. Children and people with weak immune systems may spread the virus for a longer period of time.
Most people will recover within a week to 10 days. Some people are at greater risk of complications, which include pneumonia, ear infections, sinus infections, dehydration and worsening of chronic medical conditions, such as heart disease, asthma, and diabetes. Each year in Canada, about 12,200 people are hospitalized and 3,500 die due to flu and its complications.
Those at high risk of flu-related complications or hospitalization include:
It can be hard to tell the difference between flu symptoms and other respiratory viruses, such as COVID-19 and Respiratory Syncytial Virus (RSV).
Common symptoms include:
Other symptoms include:
The flu vaccine is recommended for everyone six months of age and older. Getting the flu vaccine each year is the best way to protect against serious illness. Even if you had flu in the past, it’s important to get vaccinated every fall as protection can decrease over time and vaccines are updated each year to try to match the new strains expected to spread.
While vaccination is the most important step you can take to protect yourself and others, there are more steps we can all take to reduce virus spread. Using layers of protection will help protect you, loved ones and those most vulnerable in our community, such as young children and the elderly.
It can be difficult to tell flu from other respiratory viruses as the symptoms are similar. If a health care provider needs to know if you are sick with flu, they can test for it by swiping the inside of your nose with a swab to collect the virus and send it to a lab.
Most healthy people who get flu will not need medical treatment. Antiviral drugs are prescription drugs that may be used to lessen symptoms and prevent complications. Antiviral drugs are usually used early to treat hospitalized patients, people with severe influenza illness, and people who are at higher risk for complications based on their age or other health conditions.
Some high-risk individuals are eligible for COVID-19 and/or flu treatment if they have a confirmed infection. Get tested if you develop symptoms of a respiratory virus and talk to your health care provider.
Seek medical care if your symptoms feel worse than a common cold by calling your health care provider or 811 
(TTY: 1-866-797-0007). If your symptoms are severe, seek immediate medical attention.
If you have symptoms of a respiratory virus/flu, you can:
Seek medical attention if you need it. Tell the health care provider about your symptoms ahead of time and wear a well-fitting mask when you go out if you’re able to.
See the Ontario College of Family Physicians tips on caring for children with respiratory symptoms, including how to help support your sick child at home and when to call a health care provider.
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