Flu (influenza)

Influenza is commonly known as the flu. It affects people of all ages. It is especially serious for babies and older people. Vaccination is the best protection against the flu.

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What is the flu?

Influenza is commonly known as the flu. It is a very contagious infection of your airways. The flu usually causes the most disease during winter.

The flu can produce mild symptoms such as a runny nose, headache, body aches and tiredness. It can also be very severe and cause disease, including:

  • pneumonia
  • inflammation of the brain, heart, or other muscles
  • damage to organs such as the kidneys
  • death.

The flu is caused by the influenza virus. There are lots of different strains of flu virus, and they can change every year.

What are the symptoms of flu?

Symptoms usually start about one to three days after catching the flu, and can last for a week or more. Some people get no symptoms or only mild symptoms, while others can become seriously ill.

Symptoms of the flu include:

  • runny nose or sneezing
  • cough or sore throat
  • fever and chills
  • headache
  • body aches
  • vomiting and diarrhoea (more common in children).

The flu is a serious disease because it can lead to:

  • bronchitis
  • croup
  • pneumonia
  • ear infections
  • heart and other organ damage
  • brain inflammation and brain damage
  • death.

Who is at risk from flu?

The flu can affect people of all ages.

People at highest risk of being hospitalised with flu are:

  • babies
  • people more than 65 years old
  • Aboriginal and Torres Strait Islander people
  • pregnant women (and the unborn baby)
  • people with long-term medical conditions
  • people who have weakened immune systems
  • people who are obese
  • people who smoke
  • people who haven’t been vaccinated against the flu.

Long-term medical conditions that can lead to you having a serious case of the flu include:

  • heart disease
  • Down syndrome
  • lung disease
  • conditions of the nervous system (such as multiple sclerosis)
  • liver disease
  • kidney disease
  • diabetes
  • blood diseases
  • metabolic disorders.

People who have been immunised against the flu can still get the disease, but vaccination does reduce the risk and the severity of illness.

How do you get flu?

The flu can spread:

  • when an infected person coughs or sneezes and another person breathes it in
  • through direct contact with fluid from an infected person’s coughs or sneezes
  • by touching a contaminated surface with the flu virus on it, and then touching your mouth, eyes or nose.

The flu spreads easily through families, workplaces, childcare centres and schools.

How do you prevent flu?

Vaccination is the best protection against the flu.

The flu vaccines protect you from getting infected and prevent serious disease. The flu strains constantly change so you need a new vaccine every year to make sure you stay protected.

For more information on immunising against flu, see Flu immunisation service.

If you have the flu, you can help stop the disease spreading by:

  • staying away from childcare, school, work or other places where they could spread the infection until you are well
  • covering your coughs and sneezes
  • washing your hands often.

How do you know you have flu?

If you think you or one of your family members has the flu, see your doctor.

Your doctor will ask about your symptoms and whether you’ve been in contact with someone who has the flu. If your doctor thinks you have the flu, they may swab your nose or throat, or take a blood sample to test for the virus.

How do you get treated for flu?

Mild flu gets better on its own without any treatment.

You can relieve the symptoms by:

  • resting
  • taking paracetamol to reduce pain and fever
  • using decongestant medicines.

People with a serious case of the flu may need to go to hospital. Even with treatment, some people with severe flu may die.

If diagnosed, you may be given medicines which if given early can help shorten how long illness lasts.

More information

See more information on vaccines available to protect against diseases covered under the National Immunisation Program.


If you need advice or more information about immunisation, go to our How do I immunise my child?  page or our main Immunisation contacts page.

Page last updated: 30 Mar 2022