Influenza, also called the flu, is an infection of the upper airway caused by an influenza virus. Symptoms can include fever, headache, runny nose, sore throat, or cough. Every year there is a period of time where there are more outbreaks of the flu, this is called flu season. Flu season generally occurs during the fall, winter and early spring. The influenza vaccines protect against the viruses that cause influenza. To learn more about the flu and the flu vaccines, and to access flu-related information from your health authority, visit our Influenza (Flu) Season health feature.
A bacterial infection may develop following infection with viral
influenza. Signs of a bacterial infection
pain that lasts more than 24 hours or severe ear pain that lasts longer than 1
A sore throat that lasts longer than 2 to 3 days despite home
treatment and does not "act" like a cold.
Sinus pain that persists
despite 2 to 4 days of home treatment, especially if nasal drainage is coloured
rather than clear and fever is also present.
Nasal drainage that
changes from clear to coloured after 5 to 7 days of flu, while other symptoms
(such as sinus pain or fever) are getting worse.
A cough that
lingers more than 7 to 10 days after other symptoms have cleared, especially if
it is bringing up mucus (productive).
Yellow, green, rust-coloured, or bloody mucus that
is coughed up from the lungs, especially while other symptoms are getting
worse. Mucus coughed up from the lungs is a more serious symptom than mucus
that has drained down the back of the throat (post-nasal drip).
These infections may sometimes need treatment with