Influenza – Commonly called "the flu"
One of the best ways to prevent seasonal influenza is through immunization. It is important to be immunized every year because the influenza virus is always changing and influenza vaccine is different every year.
What is influenza?
Influenza, commonly called the flu, is a respiratory disease that affects the nose, throat and lungs. It is caused by a virus that is easily passed from person to person.
- Seasonal influenza is the annual influenza that affects people in Canada during the winter, between November and April.
- Seasonal influenza viruses change slightly from year to year.
- Various strains of influenza virus circulate throughout the world each year and new strains can emerge and spread.
- Most healthy people are able to recover from influenza without severe complications.
- As with other viral illnesses, antibiotics do not work against an influenza virus. Antiviral medications may be used for treatment or prevention of influenza.
Influenza lowers the body’s ability to fight other infections. It can lead to bacterial infections, such as pneumonia, and even death especially in the elderly, children (6–59 months), pregnant women, Aboriginal peoples, and people with chronic medical conditions.
How is influenza spread?
Influenza spreads rapidly among people.
- The virus passes from person to person when an infected person coughs, sneezes or talks. Tiny drops of moisture (droplets) containing the virus can enter the eyes, nose or mouth of people nearby.
- The virus can live on hands and is then passed to surfaces through touching. The virus can live on hard surfaces such as door handles, telephones, light switches, computer keyboards, countertops for up to 48 hours, and on soft surfaces like clothing for 8–10 hours.
- Infection can happen when people touch any surface contaminated with the virus and then touch their own mouth, nose or eyes before washing their hands.
- People usually develop symptoms of influenza within four days after becoming infected.
- People are contagious for seven days after symptoms start.
- Children, especially younger children, individuals with weakened immune systems and those with severe illness may be contagious for a longer period, i.e., up to 10 days .
How can influenza disease be prevented?
One of the best ways to prevent seasonal influenza is to get immunized with the seasonal influenza vaccine every year. It is safe and effective.
To protect yourself from all strains of influenza:
- Clean your hands often with soap and warm water, or hand sanitizer.
- Eat nutritious food, exercise, and get a good night’s sleep to stay as healthy as possible.
- Cover your cough in your sleeve.
- Stay at home when you are sick.
How serious is influenza?
Certain people can develop serious health problems from influenza, such as pneumonia, which may cause death. These include:
- children younger than 5 years of age and adults 65 years of age and older;
- people with weakened immune systems;
- people with certain chronic illnesses, such as heart, lung or kidney disease, diabetes and cancer;
- those who are severely overweight;
- pregnant women;
- Aboriginal peoples.
Influenza can also make other health conditions such as diabetes, lung disease, heart disease, kidney disease and cancer worse.
Every year, influenza and the health problems it causes have a significant effect on the health-care system. It also affects school or work absenteeism.
What is avian influenza or bird flu?
Avian influenza is a contagious viral infection affecting all species of birds and sometimes mammals. On rare occasions it can be spread to humans through close contact with infected birds.
What is an influenza pandemic?
An influenza pandemic (worldwide flu) is declared when a new strain of influenza virus that has never been seen before emerges and begins to spread quickly around the world. The pandemic phase level indicates the spread of the virus around the world, not how severe the virus is.
- People have little or no natural immunity, so large numbers of people become ill.
- Occurs 3–4 times each century, which last occurred in 2009 as Pandemic (H1N1) 2009.
People develop symptoms of influenza from 1–4 days after becoming infected. They can pass on the virus from the day before they have the first symptoms until at least 5–7 days after the symptoms start.
- Fever of 38 C (100.4 F) or higher that starts suddenly;
- A dry cough that can last for weeks;
- An aching body especially in the lower back and legs;
- Feeling very weak and tired.
Other symptoms can include:
- Loss of appetite;
- Sore throat;
- Runny or stuffy nose;
- Some people may have nausea, vomiting and diarrhea.
- Individuals younger than 5 years of age or those 65 years of age and older may not have a fever.
- Fever usually goes down and the person starts to feel better in 3–5 days. However, exhaustion and cough can continue for several weeks.
- Symptoms in babies may be hard to detect. For some babies, crying more than usual may be the only sign of illness.
- Influenza symptoms are different from those of a cold or a stomach upset.
The influenza self-care section has information to help take care of yourself and others who have influenza.
- Read about influenza self-care
- What is the difference between influenza, a cold and stomach upset? – Comparison chart
If you have more questions, contact Health Link at 811.