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.
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.
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 6 to 59 months of age, pregnant women, people 65 years or older, and people with chronic health problems. 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.
The symptoms of influenza are fever of 38.5°C (101.3°F) or higher that starts suddenly, 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.
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
Involves whole body
Symptoms appear quickly
No. Symptoms appear gradually.
Yes, and can be severe
Chills, aches, pain
Yes, and often severe
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: September 1, 2017
Author: Influenza Immunization Program, Alberta Health Services
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