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Influenza

Influenza

What causes flu?

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

  1. influenza A
  2. influenza B

How is flu spread?

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 to others by:

  • sneezing
  • coughing
  • talking

These actions release tiny droplets containing the flu virus into the air.

You can become infected if these droplets land on your:

  • nose
  • mouth
  • eyes

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

  • doorknobs
  • phones
  • television remotes
  • someone’s hands

What are the symptoms of flu?

Some people get mildly ill, while others get very sick.

Flu symptoms usually include the sudden appearance of:

  • high fever (39°C and above)
  • cough
  • muscle aches

Other common symptoms include:

  • headache
  • chills
  • loss of appetite
  • fatigue (tiredness)
  • sore throat
  • runny or stuffy nose

Some people, especially children, may also experience:

  • a stomach ache
  • diarrhea
  • nausea and vomiting

It takes 1 to 4 days for flu symptoms to appear after exposure to the virus.

Most people recover from the flu in 7 to 10 days. Others may develop serious complications, such as pneumonia (a lung infection), and may need hospital care.

Differences between the flu and a cold

A cold infects just your nose and throat, while the flu also affects your lungs.

Cold symptoms are unpleasant but are usually milder than the flu. They include:

  • runny nose
  • sneezing
  • cough
  • sore throat

Read more about how to tell if you have a cold or the flu.

What do you do if you become ill?

If you are mildly ill, stay home and avoid contact with other people until your symptoms are gone. This will help prevent the spread of the virus.

If you are a person at high risk of flu-related complications, contact your health care provider. Tell them about your symptoms.

See a health care provider immediately if you develop any of these symptoms:

  • shortness of breath
  • fast or trouble breathing
  • pain in your chest
  • blueish or grey skin colour
  • bloody or coloured mucous in your mouth or spit
  • sudden dizziness or confusion
  • severe or ongoing vomiting
  • a high fever (39°C and above) that lasts more than 3 days

Tell your health care provider about your flu symptoms over the phone before your appointment. That way, they can arrange to see you without exposing other people to the virus.

Also see a health care provider if you are caring for a child who is sick with the flu and is:

  • not drinking or eating as usual
  • not waking up or interacting with others
  • irritable (not wanting to play or be held)

What are the risks of getting the flu?

Anyone can get the flu if they are exposed to the virus.

Canada

In Canada, your risk of getting the flu is higher in the late fall and winter months. The risk is lower during the rest of the year.

The flu is ranked among the top 10 leading causes of death in Canada.

Each year in Canada, it is estimated that the flu causes:

  • 12,200 hospital stays
  • 3,500 deaths

Worldwide

Every year, worldwide outbreaks cause an estimated:

  • 1 billion cases of flu
  • 3 to 5 million cases of severe illness
  • about 250,000 to 500,000 deaths

The flu usually occurs in:

  • the northern hemisphere between November and April
  • the southern hemisphere between April and October
  • tropical countries during the entire year

The following activities may increase your chance of getting the flu:

  • crowded conditions or attending large group events or gatherings
  • travelling on cruise ships or joining large commercial tours

Who is most at risk?

Some people are more likely to get flu-related complications (like pneumonia) or be hospitalized because of complications. These include:

  • people with health conditions, such as:
    • cancer
    • diabetes
    • heart disease
    • lung disease
    • obesity
  • people 65 years and older
  • people who live in nursing homes or other long-term care facilities
  • children under 5 years of age
  • pregnant women
  • Indigenous peoples

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

  • those who are in close contact with the listed higher risk groups, such as:
    • family
    • household members
    • caregivers
  • those who care for or are expecting a newborn baby during flu season
  • health care workers
  • child care workers
  • those who provide services to people at high risk in closed settings, such as crew on a ship

How is flu diagnosed?

The flu is usually diagnosed by a health care provider based on:

  • symptoms
  • laboratory tests

How is flu treated?

Be aware of the symptoms of the flu and what to do if you get sick.

Mild flu symptoms can be treated with:

  • rest
  • fluids
  • medicine to reduce any fever or aches

Over-the-counter cough and flu medicine should not be given to children younger than 6 years old. It is only safe to do so if advised by your health care provider.

Your health care provider may prescribe an antiviral drug if you are:

It is important to start antiviral medication as soon as possible.

How can flu be prevented?

The best way to prevent the flu is by getting a flu vaccine, also known as a flu shot. Flu vaccine is safe and effective. You cannot get the flu from the flu vaccine. Most people do not have reactions to the flu vaccine. Severe reactions are very rare.

Getting a flu vaccine is a simple action that can save lives by:

  • protecting you if you are exposed to the virus
  • preventing you from getting very sick
  • helping protect other people because you are less likely to spread the virus to others

Everyone 6 months and older should get the vaccine. This is especially important for:

It is important that you get a new flu vaccine every year because the:

  • effectiveness of the vaccine can wear off, so you need a new one every year to stay protected
  • type of flu virus usually changes from year to year
    • experts create a new vaccine to protect you each flu season

Ask your health care provider about getting the vaccine. You can also find a location near you (such as a pharmacy or public health clinic) to get the vaccine.

This season’s flu vaccine will protect against the influenza viruses that research indicates will be most common during the season. This includes:

  • 2 influenza A viruses
  • 1 or 2 influenza B viruses, depending on the flu vaccine you receive

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

  • washing your hands frequently
  • coughing and sneezing into the bend of your arm, not into your hand
  • avoiding touching your nose, mouth or eyes with your hands
  • cleaning and disinfecting objects and surfaces that a lot of people touch, such as:
    • doorknobs
    • phones
    • television remotes
  • eating healthy foods and doing physical activities to keep your immune system strong
  • getting plenty of rest or sleep

If you do get sick, stay home and avoid contact with other people until your symptoms are gone. This will help prevent the spread of the virus.

If you plan to travel, consult a health care provider or travel health clinic at least 6 weeks before leaving.

Source:© All rights reserved. Causes of Flu (Influenza). Public Health Agency of Canada, 2015, with permission from the Minister of Health, 2017.

Source:© All rights reserved. Symptoms of Flu (Influenza). Public Health Agency of Canada, 2015, with permission from the Minister of Health, 2017.

Source:© All rights reserved. Risks of Flu (Influenza). Public Health Agency of Canada, 2015, with permission from the Minister of Health, 2017.

Source:© All rights reserved. Treatment of Flu (Influenza). Public Health Agency of Canada, 2015, with permission from the Minister of Health, 2017.

Source:© All rights reserved. Treatment of Flu (Influenza). Public Health Agency of Canada, 2015, with permission from the Minister of Health, 2017.