What is influenza?
Influenza (flu) is a lung infection caused by specific influenza viruses. People can get the flu at any time of year, but it is more common in the fall and winter.
Common symptoms of the flu
People who get the flu usually have some or all of the following symptoms:
- fever
- muscle aches
- headache
- sore throat
- cough
- fatigue and weakness
Most of these symptoms usually last for two to seven days. Rare but serious complications of the flu include bacterial pneumonia and influenza infection of the brain.
The flu can be serious for some people
Most people who have the flu will not become seriously ill. But the flu can be more serious for some people. Typically, those most at risk are in one of the following groups:
- Children under two years of age
- People 65 years of age or older
- People living in long-term care facilities such as a nursing home, a home for the aged or a chronic care hospital
- People with chronic heart, lung or kidney disease
- People with diabetes, cancer, immune system problems or sickle cell anaemia
- Children and teenagers aged six months to 18 years who have been treated with acetylsalicylic acid (ASA) for long periods
- People who have trouble clearing mucus from their nose and throat because of weakness or underlying illness
These groups, and anyone who lives or works with people from these groups, should generally be immunized each year with the flu vaccine (flu shot). That way, people from these high-risk groups are less likely to be infected with the flu.
How the flu spreads
The flu spreads very easily from an infected person to others through coughing and sneezing. It is also spread by touching objects after someone with the flu has touched them.
Treating the flu
If you or your child have the flu, stay home and rest. Usually, treatment is focused on the symptoms the person is feeling. For example, if your child has a fever, you can give them acetaminophen or ibuprofen to reduce fever.
For information on how to safely use acetaminophen or ibuprofen tablets by mouth for children please see this information sheet.
Do not give acetylsalicylic acid (ASA) to a child under 16 years of age. Do not give cough medicines to children under six years of age. Always read the label before giving any medicine.
In addition to fluids and pain medicine, other ways to treat flu symptoms include:
- applying heat on painful areas for short periods of time using a hot water bottle or heating pad to reduce muscle pain
- taking a warm bath
- gargling with a glass of warm water
- using saline drops or spray and suction to clear a stuffy nose
- keeping your home smoke free
Call your child’s primary care provider if the above measures do not relieve your child's flu symptoms and your child feels worse or if you are worried.
If your child has the flu in the hospital
Your child will be placed in a single room and will not be able to visit the playroom until they are feeling better. Ask the child life specialist to bring toys and supplies to your child’s room.
Hospital staff will be wearing a mask, eye protection, gloves and gowns when they visit.
Wash your hands often, either with alcohol-based hand rubs or soap and water, before and after touching your child and before leaving your child's room. Hospital staff should wash their hands as well.
If you or anyone else who has visited becomes ill with symptoms of the flu, let your child's doctor or nurse know.
Preventing the flu
To help prevent the flu, it is important that you and your child get a flu shot every year.
You should also wash your hands well. This can help prevent you from catching or spreading the flu. This is very important in hospitals, but it is true in other places as well.
Clean surfaces in your house regularly, especially ones you touch often. These include doorknobs, fridge doors, light switches, phones and computers.
If you have the flu, you should do the following things to avoid spreading it.
- Always cover your mouth and nose with a tissue when you cough or sneeze. Throw away the tissue, then wash your hands. These steps will help prevent spreading the flu and other respiratory viruses.
- Do not visit the hospital when you are sick with symptoms of the flu. No one who is sick should visit a patient in the hospital, even if they are a relative.
The flu shot
Does the flu shot really work?
For more videos from SickKids experts in collaboration with Youngster, visit Youngster on YouTube.
The influenza vaccine (flu shot) is made from pieces of killed or live but weakened flu viruses. It contains three or four different types of flu viruses. A person who receives the flu shot develops immunity for the types of flu in the vaccine. Immunity means the body builds up protection against the virus.
The body needs about two weeks after the shot to build up protection against the virus. This protection lasts for about six months.
The flu shot will not protect against other viruses, such as viruses that cause the common cold.
For tips on how to make vaccinations as easy and pain-free as possible, please read the articles,
Needle pokes: Reducing pain in infants aged up to 18 months and
Needle pokes: Reducing pain in children aged 18 months or over.
A flu shot every year
People need a new flu shot every year. The flu virus changes each year, so a different vaccine has to be used each year too. Doctors and scientists find out the types of flu virus that are circulating around the world. The vaccine is then made to protect against the types that are most likely to occur each year.
Most people can get a flu shot
The flu shot is free to people living in Ontario. Anyone older than six months of age should have the flu shot unless there is a reason not to. The best time to get the flu shot is in the fall, before the flu becomes more common. Ask your child's primary care provider if your child can get the flu shot.
The flu shot and COVID-19
It is more important than ever to get a flu shot during COVID-19. Getting the flu shot can help to reduce unnecessary testing for COVID-19, since symptoms of both illnesses are similar. It is also important to reduce your and your child’s chances of getting the flu in order to avoid trips to the doctor’s office or hospital. This will help to make sure that doctor’s offices and hospitals are not overwhelmed with flu cases while also treating COVID-19 cases.
The flu shot will not protect against COVID-19, therefore it is still important to wear a mask, perform hand hygiene and maintain a physical distance of 2 metres from those who are not in your social circle.
When to seek medical attention
Go see a doctor or to hospital if your baby is less than three months old and:
- has a fever
- has fast or difficult breathing
- is vomiting or not feeding
Go see a doctor if your child:
- is more sleepy than usual
- is more fussy than usual
- is not drinking enough fluids or has not peed at least every six hours when awake
- is vomiting
- is having chest or stomach pain
- is not feeling better after five days or gets better but then suddenly gets worse
Call 911 or go to the nearest emergency department immediately if your child:
- is breathing quickly, or seems to be working hard to breathe
- is very weak, dizzy, hard to wake up or does not respond well
- is very fussy or cannot be comforted
- is limping or refusing to walk
- has bluish or dark-coloured lips or skin
- has a stiff neck, severe headache or a seizure
- has a very fast heart rate, even when the fever is down
If you have any concerns, call your doctor or your local public health agency. In Ontario, you can also call Health811 (811 | TTY: 1-866-797-0007).
If you or your child is in a high-risk group, call your doctor right away when you get flu symptoms. There are specific anti-viral medicines available to help treat flu. These medicines must be started early in the illness to be effective. Contact your child's doctor for more information.