Facts about influenza (the flu)

Facts about influenza (the flu)

Last updated: September 16, 2022
Influenza (Flu) Series
HealthLinkBC File Number: 12b
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What is influenza?

Influenza is an acute infection of the respiratory system caused by the influenza virus.

Getting sick with influenza also puts you at risk of other infections. These include viral or bacterial pneumonia which affect the lungs. The risk of complications can be life-threatening. Seniors 65 years and older, infants and very young children, people who have lung or heart diseases, certain chronic health conditions or weakened immune systems are at much greater risk.

Healthy pregnant women in the second half of their pregnancy are at much greater risk of hospitalization following infection with influenza virus.

In Canada, thousands of people are hospitalized and may die from influenza and its complications during years with widespread or epidemic influenza activity.

How can you prevent influenza?

You can reduce the risk of getting influenza and spreading it to others by:

  • Getting an influenza vaccine
  • Staying home when you are ill
  • Washing your hands regularly
  • Cleaning and disinfecting objects and surfaces that people touch
  • Promptly disposing of used tissues in the waste basket or garbage
  • Cough and sneezing into your shirt sleeve rather than your hands

Getting an influenza vaccine can help prevent you from getting sick with influenza and spreading it to others.

How does influenza spread?

Influenza spreads easily from person-to-person through coughing, sneezing or having face-to-face contact. The virus can also spread when you touch tiny droplets from a cough or sneeze on another person or object, and then touch your own eyes, mouth or nose before washing your hands.

You can spread the influenza virus even before feeling sick. An adult can spread the virus from about 1 day before to 5 days after symptoms start. Young children may be able to spread the virus for a longer period of time.

What are the symptoms?

Influenza symptoms vary from mild to severe, and can include:

  • Fever,
  • Headache,
  • Muscle pain,
  • Runny nose,
  • Sore throat,
  • Extreme tiredness
  • A cough

Children may also experience nausea, vomiting or diarrhea. Although infections from other viruses may have similar symptoms, those due to the influenza virus tend to be worse with a greater risk of complications.

Symptoms can begin about 1 to 4 days, average of 2 days, after a person is first exposed to the influenza virus. Fever and other symptoms can usually last up to 7 to 10 days, but the cough and weakness may last 1 to 2 weeks longer.

How can you treat influenza symptoms at home?

If you get sick with influenza, treating symptoms can help. Follow the self-care advice below:

  • Get plenty of rest and stay home from work, school, daycare and running errands when you are sick
  • Drink extra fluids to replace those lost from fever
  • Avoid smoking and ask others not to smoke in the house
  • Breathe moist air from a hot shower or from a sink filled with hot water to help clear a stuffy nose
  • Anti-influenza drugs or antivirals are available by prescription, but these must be started within 48 hours of the start of your symptoms to work best. These will shorten symptoms by about 3 days if given within 12 hours and by about 1.5 days if given within 2 days of the start of symptoms
  • Non-prescription cough and cold medications are available for relief of influenza symptoms but are not recommended for children under 6 years old
Acetaminophen (e.g. Tylenol®) or ibuprofen* (e.g. Advil®) can be given for fever or soreness. ASA (e.g. Aspirin®) should not be given to anyone under 18 years of age due to the risk of Reye syndrome.

*Ibuprofen should not be given to children under 6 months of age without first speaking to your health care provider.

For more information on Reye syndrome, see HealthLinkBC File #84 Reye syndrome.

When should I see a health care provider?

Consult your health care provider if you have a condition that puts you at higher risk of complications and you develop influenza-like symptoms.

You should also call your health care provider if your symptoms get worse, such as shortness of breath or difficulty breathing, chest pain or signs of dehydration (such as dizziness when standing or low urine output).

Is it influenza or a cold?

The following table can help you determine whether you have influenza or a common cold.

Symptoms Common Cold Influenza (the flu)
Fever Rare Usual, sudden onset 39º to 40ºC (102.2 to 104ºF), lasts up to 3 to 4 days
Headache Rare Usual, can be severe
Aches and pains Sometimes mild Usual, often severe
Fatigue and weakness Sometimes mild Usual, may last 2 to 3 weeks or more
Extreme fatigue Unusual Usual, early onset, can be severe
Runny, stuffy nose Common Sometimes
Sneezing Common Sometimes
Sore throat Common Sometimes
Chest discomfort, coughing Sometimes mild to moderate Usual, can be severe
Complications Can lead to sinus congestion or earache Can lead to pneumonia, respiratory failure, and more complications in persons with chronic diseases
Prevention Frequent hand washing Yearly influenza vaccine and frequent hand washing
Treatment No specific treatment is available; symptom relief only Antiviral drugs by prescription, which can reduce severity of symptoms and duration

For more information

For more information, see the following HealthLinkBC Files: