Flu (seasonal influenza): Spread, prevention and risks
Seasonal influenza, often referred to as the flu, is a contagious viral respiratory illness.
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How the flu spreads
The flu is an infection of the nose, throat and lungs.
It spreads very easily from person to person. Someone who has the flu can spread the virus to others even before they notice any symptoms.
You can get the flu if:
- you breathe in the infectious particles
- the infectious particles or secretions (like saliva or mucus) come into direct contact with your eyes, nose or mouth
- for example, when someone with the flu coughs or sneezes on you
- you touch your eyes, nose or mouth with unclean hands after you've touched infectious particles or secretions on:
- a contaminated surface or object
- another person (for example, through a handshake)
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Preventing the flu
Vaccination
The flu vaccine (flu shot) is the best way to prevent the flu and its complications. Though a sore arm can be common, most people don't have any other side effects. Severe reactions are very rare.
You can't get the flu from the flu vaccine.
The flu vaccine is recommended for almost everyone 6 months of age and older. You need a flu vaccine every year because:
- protection from the vaccine decreases over time
- the flu viruses that circulate can change from year to year
If you have questions about the flu vaccine, talk to:
- a health care provider, such as a doctor, nurse or pharmacist
- your local public health unit or office
- the person giving you the vaccine
Learn more:
- Get your flu vaccine
- Vaccine safety and possible side effects
- Vaccine safety: Immunization and vaccine awareness poster
- HELP Eliminate Pain in Kids and Adults (University of Toronto)
Personal protective measures
In addition to getting the flu vaccine, you can reduce your risk of getting or spreading the flu by:
- staying home and limiting contact with others when you're sick, even if your symptoms are mild
- wearing a well-fitting respirator or mask
- wearing a mask is recommended if you have symptoms and must:
- be around others
- enter a public setting
- seek medical care
- wearing a mask is recommended if you have symptoms and must:
- opening windows and doors when possible to improve indoor air ventilation
- cleaning your hands regularly by:
- washing with soap and water for at least 20 seconds (preferred method if hands are visibly soiled) or
- using a hand sanitizer containing at least 60% alcohol for 20 seconds or until dry
- covering your coughs and sneezes with a tissue or your elbow instead of your hand
- avoiding touching your eyes, nose or mouth with unclean hands
- cleaning and disinfecting high-touch surfaces and objects regularly
Learn more:
- Clean your hands to help reduce the spread of infectious diseases
- Respiratory infectious diseases: Reduce your risk with personal protective measures
Risks of getting the flu
In Canada, your risk of getting the flu is higher in the late fall and winter (flu season). It's lower during the rest of the year.
The flu is among the 10 leading causes of death in Canada. Every year in Canada, the flu causes about:
- 15,000 hospital stays
- 3,500 deaths
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Who is most at risk
Certain people are at an increased risk of being exposed to the flu, developing serious flu-related complications, or both.
Others may not be at an increased risk of complications, but they work with, live with, care for, or regularly interact with people who are. These individuals are generally health care or child care providers. If these individuals become infected with the flu, they may spread the virus to those who are at higher risk of complications.
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Younger children
Children under 5 years of age are more likely to be exposed to the flu in certain settings that are higher risk for spreading the flu, such as:
- daycare
- preschool
- school
Children under 5 years of age are also at greater risk of getting the flu. Their immune systems are still developing the ability to fight off serious infections.
People with health conditions
You're at a higher risk of flu-related complications if you have a health condition, such as:
- heart or lung disorders
- diabetes or other metabolic diseases
- cancer or other conditions that compromise the immune system
- kidney disease
- anemia or certain other blood disorders
- neurological or neurodevelopmental conditions
- severe obesity (body mass index of 40 kg/m² and over)
- a condition that requires treatment for long periods with acetylsalicylic acid (ASA) and you're 18 years of age or younger
Getting the flu can also worsen the symptoms of some of these health conditions.
Pregnant people
Pregnant people are at higher risk of serious complications from the flu. Infection during pregnancy can also have negative outcomes for the developing baby.
Getting the flu vaccine in pregnancy is safe and the best way to protect yourself against severe disease. If you get the flu vaccine during pregnancy, you also pass on protection to your baby. This helps protect your baby before and after birth. This is especially important as babies younger than 6 months old:
- are at the highest risk for complications
- can't get vaccinated against the flu
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People in group living settings
People who live in a nursing home or other long-term (or chronic) care facility may be more at risk of being exposed to the flu. This is because it can spread quickly in communal living spaces.
Residents of such settings are also more likely to have chronic health conditions, which can increase the risk of serious flu-related complications. These chronic conditions can also get worse when infected with the flu.
Older adults
You're at higher risk of getting the flu and having more serious complications if you're 65 years of age and older.
Your immune system changes with age and this can make it harder for your body to fight off infections. Compared to younger adults, people 65 years of age and older are more likely to have severe outcomes from the flu. These may lead to hospitalization or death.
Individuals in or from First Nations, Inuit or Métis communities
Some Indigenous Peoples can have a higher risk of severe flu because of the historical and ongoing impacts of colonization and systemic racism. These impacts can affect living conditions and make it harder to access timely, appropriate and culturally safe health care. Together, these factors can increase the risk of severe flu.
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