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Common Questions about Influenza Symptoms

​​​​What is influenza?

Influenza 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 about 12,200 people to be admitted to the hospital and about 3,500 deaths in Canada each year. There is a higher risk of getting complications from influenza for children less than 5 years of age, pregnant women, people 65 years or older, people with chronic health problems, people living in long term care facilities, and indigenous persons. Complications of influenza can include pneumonia, ear and sinus infections, and dehydration. Influenza can also make chronic medical problems (e.g., congestive heart failure, asthma, diabetes) worse.

What are the symptoms of influenza?

The symptoms of influenza are fever of 38.5°C (101.3°F) or higher that starts suddenly, sore throat, runny nose, cough, headache, muscle aches, loss of appetite, and feeling tired.

People can spread (are contagious) influenza the day before they have symptoms and for 5 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.
  • 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 are sick.

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

Seasonal Influenza

Common Cold

Stomach "Flu"

Caused by

Influenza A or Influenza B viruses

Many different kinds of viruses such as rhinovirus, coronavirus, adenovirus, etc. NOT CAUSED BY INFLUENZA VIRUS

Norovirus (or Norwalk-like viruses) is the most common; however, there are many causes of stomach upset. NOT CAUSED BY INFLUENZA VIRUS


Annual influenza immunization protects against the strains of influenza virus circulating that season

Cannot be prevented by immunization

Cannot be prevented by immunization

Involves whole body




Symptoms appear quickly


No. Symptoms appear gradually.



Yes, and can be severe



Chills, aches, pain

Yes, and often severe



Extreme tiredness

Yes, and may last two to three weeks or more




Yes. High fever, beginning suddenly and lasting three to four days, is common








Current as of: October 4, 2019

Author: Influenza Immunization Program, Alberta Health Services