About influenza (flu)
Influenza, commonly called the flu, is a contagious respiratory infection caused by influenza viruses that infect the nose, throat and lungs.
Higher-risk groups
Some people are at higher risk of severe influenza illness, including:
- young children;
- pregnant individuals;
- older adults; and
- people with certain health conditions.
Symptoms and severity
Influenza is typically more severe than the common cold. Symptoms often develop suddenly and can make people feel very ill.
- Most people recover within 7 to 10 days.
- Influenza can cause serious illness and may require hospitalization.
- In some cases, influenza can be life-threatening.
Flu season
Flu season generally runs from October to April.
Because influenza viruses change over time, influenza vaccines are updated regularly to protect against the strains expected to circulate each season.
How influenza spreads
Influenza spreads through respiratory droplets when an infected person:
- coughs;
- sneezes;
- speaks; or
- breathes.
It can also spread when a person touches contaminated surfaces or objects and then touches their mouth, nose, or eyes.