The flu is a highly contagious illness caused by the influenza virus. The influenza virus causes infections of the nose, throat and lungs.

In most people, the flu is uncomfortable and tiring. It can keep people in bed for days or even a couple of weeks. Some people are more at risk for serious complications from the flu, including seniors, young children, and people with long-term lung diseases like asthma and chronic obstructive pulmonary disease (COPD). Flu can make asthma symptoms worse and cause COPD flare-ups.

The flu can be fatal. Each year, regular seasonal flu causes around 4500 deaths in Canada. 

The flu is transmitted from person to person in the form of droplets when someone infected coughs or sneezes. A person usually begins showing symptoms one to four days (average is two days) from the time of exposure to the flu virus. Adults are contagious the day prior to onset of symptoms, and for three to seven days after they first develop symptoms. Children could be contagious for more than a week.

Who is at risk?

Anyone can get Influenza, but for some people it can become a serious (even life-threatening) illness. Flu is easily spread, especially among certain vulnerable groups. Anyone belonging to a vulnerable group, as well as anyone with regular exposure to anyone in these vulnerable groups, should get the annual flu shot.

  • Children
  • Adults and children with chronic illnesses like asthma, COPD, diabetes, heart and kidney diseases
  • Pregnant women in their 2nd or 3rd trimester of pregnancy during the winter season
  • Persons over 65 years of age
  • People who have close contact with high-risk groups
  • Residents and employees of nursing homes and other chronic care facilities
  • People who live with or care for family members with chronic conditions
  • Health professionals, such as nurses, physicians, and other medical personnel
  • Medical volunteers


Learn more about Influenza in our Influenza Brochure.

Learn more about the High Dose Influenza Vaccine for people aged 65+.

Page Last Updated: 15/11/2021