Flu (influenza): Prevention and risks

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How the flu spreads

The flu is an infection of the nose, throat and lungs. It's mainly caused by 2 types of viruses:

  1. influenza A
  2. influenza B

The flu spreads very easily from person to person. Even before you notice symptoms, you may spread the virus to others. If you have the virus, you can spread it by:

  • talking
  • sneezing
  • coughing

These actions release tiny droplets that contain the flu virus into the air.

You can become infected if these droplets land on your:

  • eyes
  • nose
  • mouth

Infection can also happen if you touch any of these body parts after touching surfaces contaminated by infected droplets. Frequently touched surfaces and objects include:

  • toys
  • toilets
  • phones
  • door handles
  • bedside tables
  • television remotes
  • electronics and tablets

Preventing the flu

The flu shot is safe and is the best way to prevent the flu. Most people don't have any side effects. Severe reactions are very rare.

You can't get the flu from the flu shot. Scientists have developed different types of vaccines, which are:

  • non-live vaccines that contain killed (inactive) viruses or their parts
  • live vaccines that contain live but weakened (attenuated) viruses

Get the flu shot

Almost everyone 6 months of age and older should get the flu shot. Getting a flu shot is a simple action that can save lives by:

  • protecting you if you're exposed to the virus
  • preventing you from getting very sick
  • helping protect other people who are at higher risk of serious flu complications if they get the flu
    • this is because you're less likely to spread the virus to them
  • reducing additional burden on the health care system
  • reducing your chances of being infected with COVID-19, or another respiratory illness, and the flu at the same time
    • this could lead to more serious complications

In addition to getting the flu shot, you can also protect yourself and those around you by:

  • not touching your eyes, nose or mouth with unwashed hands
  • washing your hands often with soap and warm water for at least 20 seconds
    • if soap and water aren't available, use a hand sanitizer containing at least 60% alcohol
  • coughing and sneezing into the bend of your arm, not into your hand
  • cleaning and disinfecting surfaces that a lot of people touch, such as:
    • phones
    • doorknobs
    • television remotes
  • staying home if you're sick
    • if you start to develop symptoms, isolate yourself from others and contact a health care provider or local public health authority

It can be hard to tell the difference between symptoms of the flu and COVID-19. You can only confirm if you have flu or COVID-19 with a test. If you have symptoms of the flu and haven't received a negative COVID-19 test, follow COVID-19 prevention measures to help keep others safe.

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When the flu is a risk

In Canada your risk of getting the flu is higher in the:

  • late fall
  • winter

Your risk is lower the rest of the year.

Who is most at risk

Everyone is at risk of getting the flu. The flu is among the 10 leading causes of death in Canada. According to data from before the COVID-19 pandemic, each year in Canada, the flu causes an estimated:

  • 12,200 hospital stays
  • 3,500 deaths

Some people are at a higher risk of flu-related complications. These include:

People with health conditions

These conditions can affect a person's immune system and can make it harder to fight off infections, such as:

  • cancer and other immune compromising conditions
  • diabetes
  • heart disease
  • lung disease
  • anemia
  • obesity
  • kidney disease
  • neurological or neurodevelopmental conditions
  • children up to 18 years of age undergoing treatment for long periods with acetylsalicylic acid (ASA)

Getting the flu can also worsen the symptoms associated with some of these health conditions.

People 65 years and older

The immune system changes with age and this can make it harder for the body to fight off infections. People over the age of 65 are also more likely to have health conditions, which can worsen if they get the flu.

People who live in nursing homes or other long-term care facilities

The flu spreads quickly, especially in communal spaces. Residents are also more likely to have health conditions, which can worsen if they get the flu.

Children under 5 years of age

Because of their age, their immune system is still building immunity to fight off serious infections.

People who are pregnant

During pregnancy, the body goes through many changes that can affect the immune system, heart and lungs. These changes can make it harder for the body to fight off infections. Pregnant individuals and their fetuses, as well as infants, are at high risk of severe disease from flu.

People who get the flu shot during pregnancy pass on protection to their baby. This is especially important, as babies younger than 6 months can't get vaccinated against the flu. Getting your flu shot can help protect the developing fetus and your baby after birth from the flu. This is when they're at highest risk of complications.

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  • People who have reduced access to health care, such as vulnerable populations like those experiencing homelessness or those with disabilities
  • People who are at an increased risk of illness because of living conditions, such as those:
    • living in shelters who experience overcrowding
    • who have limited access to facilities for personal hygiene
    • with disabilities who might have limited capacity to understand or perform personal hygiene practices

Some people are more likely to spread the flu to those at high risk of complications. They include:

  • caregivers
  • child care providers
  • health care providers
  • family and other household members
  • those who provide services in closed or relatively closed settings to people at high risk, such as workers in long-term care facilities or crew on a ship

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Travel health advice

Flu season around the world

Seasonal flu happens worldwide.

In the Northern Hemisphere, flu season usually runs from November to March.

In the Southern Hemisphere, flu season usually runs between April and October.

Flu can happen year round in the tropics.

Prevention before and during travel

Before travelling, consult a health care provider or visit a travel health clinic, preferably at least 6 weeks before leaving.

Protect yourself and others from flu by doing the following.

  • Don't travel if you're sick with flu-like symptoms.
  • Get your annual flu shot.
    • Travellers should get their yearly flu shot at least 2 weeks before travelling.
      • It generally takes about 2 weeks for immunity to develop after vaccination.
    • Vaccines prepared for use in the Southern Hemisphere aren't available in Canada.
      • There may be differences between the vaccines made for the Northern and Southern Hemispheres based on the flu strains circulating in the region.
      • How well the Northern Hemisphere flu vaccine protects those travelling to the Southern Hemisphere can vary.
    • Flu vaccination is important for everyone 6 months of age and older.
      • This is particularly important for people at higher risk of serious flu complications.
  • Clean your hands often with:
    • soap under warm running water for at least 20 seconds or
    • hand sanitizer containing at least 60% alcohol (keep some with you when you travel)
  • Wear a mask if fever or respiratory symptoms develop to help prevent spreading infection to others.

Follow other flu prevention tips when travelling

People at risk of more severe flu

If you're a person at high risk of flu complications and you develop symptoms when travelling, see a health care provider. Before you make an appointment, tell them your symptoms. The health care provider may provide you with additional guidance.

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