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Influenza

Common questions about influenza symptoms

​​What is influenza?

Influenza (sometimes called the flu) is an infection of the nose, throat, and lungs (respiratory tract) that is caused by a virus. Influenza can happen any time during the year, but most cases happen in the winter months.

You may also hear influenza called flu, bird flu, or H1N1. All of these mean the same thing as influenza, and the information below applies to all of them.

How is influenza spread?

Influenza is spread through the air. The virus gets in the air when someone with the disease coughs, sneezes, or even talks. People who breathe in the virus can get sick. It can also be spread by touching objects that have been coughed or sneezed on by someone with the virus.

How serious is influenza?

Most people who get sick with influenza get better. However, influenza causes more than 12,000 people to be admitted to the hospital and about 3,500 deaths in Canada each year. You have a higher risk of complications (serious health problems) from influenza if you:

  • are less than 5 years of age
  • are pregnant
  • are 65 years or older
  • have chronic (long-term) health problems
  • live in a long-term care facility
  • are an Indigenous person

Complications of influenza can include pneumonia, ear and sinus infections, and dehydration. Influenza can also make chronic medical problems (such as congestive heart failure, asthma, diabetes) worse.

What are the symptoms of influenza?

The symptoms of influenza are:

  • fever that starts suddenly
  • chills
  • sore throat
  • cough
  • headache and muscle aches
  • loss of appetite (not feeling hungry)
  • feeling tired

Young children may also feel sick to their stomach (nausea), vomit (throw up), or have loose stool (diarrhea).

You can spread influenza (are contagious) the day before you have symptoms and for up to 7 days after symptoms start.

How can influenza be prevented?

  • Get the influenza vaccine. Influenza vaccine is a very effective way of protecting people from getting sick with influenza. You need to get immunized every year because the influenza viruses change. A new vaccine is made each year to protect against the viruses most likely to cause illness in that year. The best time to get immunized is October or November. You can get immunized any time during influenza season. The season starts in late fall and lasts through the winter.
  • Wash your hands with soap and water or clean your hands with a hand sanitizer that has alcohol in it.
  • Cover your mouth and nose with your arm or a tissue when you cough or sneeze.
  • Stay home and rest when you’re sick.

What is the difference between influenza, COVID-19, a cold, and a gastro-intestinal (GI) illness?

Seasonal Influenza

COVID-19

Common Cold

GI Illness (Stomach "Flu")

Caused by

Influenza A or Influenza B viruses

SARS-CoV-2 virus

Not caused by influenza virus

Many different kinds of viruses such as rhinovirus, adenovirus

Not caused by influenza virus

Norovirus (or Norwalk-like viruses) is the most common, but there are many causes of stomach upset.

Not caused by influenza virus

Prevention

Getting the influenza vaccine every year protects against the strains of the virus going around that season

Getting the COVID-19 vaccine provides protection from the SARS-CoV-2 virus (also known as COVID-19)

Cannot be prevented by immunization

Cannot be prevented by immunization

Involves whole body

Common

Sometimes

Never

Never

Symptoms appear quickly

Yes

Sometimes

No. Symptoms appear gradually.

Yes

Headache

Common

Common

Rarely

Sometimes​

Chills, aches, pain

Common

Common

Sometimes

Common

Extreme tiredness

Common

Common

Sometimes

Sometimes

Fever

Common

Common

Rarely

Sometimes

Cough

Common

Common

Common

No

Runny or stuffy nose

Common

Rarely

Common

No

Sneezing

Sometimes

Rarely

Common

No

Sore throat

Common

Sometimes

Common

No

Diarrhea

Sometimes (especially children)

Common

Rare

Common

Shortness of breath

Sometimes

Sometimes

No

No

Loss of smell or taste

No

Sometimes

No

No




Current as of: September 30, 2021

Author: Provincial Immunization Program, Alberta Health Services