Flu (influenza)

13-minute read

Key facts

Influenza (the flu) is a viral infection that causes fever and chills, sneezing, coughing and a sore throat.
The flu can be serious for some people, but if you are otherwise fit and healthy you usually don’t need to see a doctor.
The best way to prevent influenza is to have a flu vaccination every year.
Influenza can be diagnosed through a PCR test or a rapid antigen test (RAT).
You can treat the symptoms of mild flu by resting and drinking plenty of water.

What is the flu?

Influenza (the flu) is a very contagious viral infection. It’s a respiratory illness that can affect your nose, throat and sometimes your lungs.

There are 2 main types of influenza viruses:

influenza type A
influenza type B

Most people who have the flu are infected with the influenza type A virus. There are also many sub-types and strains.

The virus that causes COVID-19 is different from the virus that causes influenza.

Influenza infections are more serious than the common cold. They can cause major outbreaks and severe disease.

The flu is the most common vaccine-preventable disease in Australia.

Is it the cold or flu? infographic promotional tile — This infographic helps you compare cold and flu symptoms.

When is the flu season?

Influenza infections are generally most common from June to September. There is often more than one strain of influenza in the community at this time.

Flu season is also the time of year when you are more likely to stay indoors and be in close contact with other people. This makes it easier for the virus to pass between people.

You should get your annual flu vaccine anytime from April onwards. Each year the vaccine is made to match the most common strains of flu.

What are the symptoms of the flu?

The symptoms of flu may include:

fever and chills
cough
sore throat
sneezing and stuffy or runny nose
tiredness
headache
muscle aches and joint pains

Sometimes you may also have:

These symptoms are more common in children with the flu.

It’s possible to get flu even if you have been vaccinated. This may be due to your illness being caused by a flu strain not covered by this year’s vaccine.

CHECK YOUR SYMPTOMS — Use the Symptom Checker and find out if you need to seek medical help.

What causes the flu?

There are 4 types of influenza virus:

influenza A virus
influenza B virus
influenza C virus
influenza D virus

Influenza types A and B are usually the cause of seasonal flu.

Influenza C virus infections generally cause mild illness and are not thought to cause human epidemics.

Influenza D viruses mainly affect cows. They are not known to cause illness in people.

Some strains of the influenza virus can also infect other animals. Animal influenza viruses are distinct from human seasonal influenza viruses and do not easily pass between people.

Bird flu

Avian influenza, also known as ‘bird flu’, is an infectious disease that is found in birds.

Some avian influenza viruses are found in wild bird populations where they may cause only mild disease. But domestic birds, like chickens, can get very sick from these viruses.

Sometimes, some types of avian influenza can infect people. The most well-known subtype of avian influenza is called H5N1.

H5N1 has caused serious infections and even deaths in humans, but the number of cases has been few.

Bird flu usually spreads to humans through contact with an infected bird. Bird flu is not easily passed from human to human.

Swine flu pandemic

The swine flu pandemic was declared in 2009. This was caused by a new type of H1N1 flu virus that infected both animals and people.

Swine flu is mild in most people. But it can be severe for some high-risk groups, even causing death.

How is influenza spread?

Influenza is spread through droplets from your nose or throat. This can be from coughing and sneezing.

These droplets can be breathed in by someone else who may then get the flu.

The droplets can also land on surfaces. Anyone who touches these surfaces and then touches their nose or mouth can also catch the flu.

When should I see my doctor?

See your doctor if you:

are concerned about your symptoms
have a high fever (over 38 degrees Celsius)
have a cough that’s not improving
are in a high-risk group (see below)

Wear a mask when attending your medical appointment to help lower the spread of viruses to other people.

If you have mild flu-like symptoms and are otherwise fit and healthy, there is usually no need to see a doctor.

Am I in a high-risk group for influenza?

You are more likely to get very sick from influenza and need hospital care if you are:

younger than 5 years old
aged 65 years or older
an Aboriginal and/or Torres Strait Islander person
pregnant

You may also be at risk of a severe influenza infection if you have:

heart disease
a chronic lung condition, such as asthma
kidney disease
diabetes

You are also at risk of severe illness if you:

are immunocompromised (have a weakened immune system)
are homeless
live in an aged care facility.

FIND A HEALTH SERVICE — The Service Finder can help you find doctors, pharmacies, hospitals and other health services.

How is the flu diagnosed?

Your doctor will ask about your symptoms and examine you, including listening to your chest using a stethoscope.

To confirm a diagnosis of influenza, your doctor will arrange a flu test.

This involves taking a sample of cells and mucus from your nose or throat using a sterile cotton swab. This sample is then sent to a pathology laboratory for testing using a polymerase chain reaction (PCR) test. A PCR test can find the genetic material of the virus or bacteria causing your symptoms.

Your doctor may also test you for COVID-19.

Can I diagnose influenza at home?

You can diagnose flu at home using an over-the-counter rapid antigen self-test (RAT). These are like the ones used to test for COVID-19.

Some RATs can test for multiple viruses, like:

influenza A influenza B
COVID-19
respiratory syncytial virus (RSV)

How is the flu treated?

Most people will get better by themselves within 7 to 10 days and without any treatment.

Some things you can do to ease your flu symptoms are:

getting plenty of rest
drinking plenty of fluids to prevent dehydration
keeping warm

You can also take paracetamol, ibuprofen or other over-the-counter medicines to treat any pain or fever. Always follow the instructions on the packet.

Various gargles, throat sprays and lozenges are available for the relief of a sore throat. Some people find warm fluids, such as warm water with honey, or sucking ice helpful.

Anti-viral treatments

Your doctor may suggest antiviral medicines if you’re at risk of severe illness. Anti-viral medicines help to shorten the length of your illness and reduce your risk of complications.

Anti-viral treatments are most effective when given within 48 hours of you getting symptoms.

Anti-viral treatments are not usually given to healthy people aged 5 to 65 years. They are most effective for people with a high risk of complications — such as older people and people with other health conditions.

Antibiotics

Antibiotics are not generally used to treat flu. This is because antibiotics do not work for viral infections. If your doctor gives you antibiotics, they may be to treat complications of influenza.

Taking antibiotics when you don’t need them can increase the risk of antibiotic resistance in the future.

Should I stay at home?

If you are sick with the flu, stay home and avoid close contact with other people until you feel better.

If your child has the flu, keep them at home until they are symptom free.

Should I keep my child home from school?

Here’s a list of common childhood illnesses, including colds and flu, and their recommended exclusion periods.

Can the flu be prevented?

The best way to prevent the flu is to have a flu vaccination every year.

Flu vaccine

Influenza vaccines prevent against different types of influenza A and influenza B.

There are different types of influenza vaccines. Speak with your doctor about the best vaccine for you.

You should get your annual influenza vaccine anytime from April onwards. This will protect you for the peak flu season. You get the highest level of protection in the first 3 to 4 months after vaccination.

You can get the flu vaccine at the same time as you get most other vaccines.

When should I get the influenza vaccine?

You should have the flu shot every year. Most people only need one injection.

Some people need 2 shots, 4 weeks apart, these are:

children aged 6 months to 9 years old getting the flu shot for the first time
people getting the flu shot for the first time after a stem cell transplant, organ transplant or treatment called ‘CAR T-cell therapy’

To find out more read Flu vaccine FAQs.

Other ways to prevent influenza

Good hygiene is one of the best ways to help prevent flu and other illnesses from spreading. Try to:

Wash your hands regularly.
Cover your mouth and nose when coughing or sneezing.
Throw used tissues in the bin straight away.
Don't share cups, plates, cutlery and towels with other people.

Influenza is an airborne disease. The virus is spread when people talk, cough and sneeze. Wearing a face mask can help lower your chance of catching the flu.

If you are sick, you can:

avoid touching your eyes, nose and mouth
stay at home

The Immunisation Coalition has produced the video below, which explains influenza. It talks about:

how contagious the flu virus is
how long the virus lasts
what can be done to prevent infection

Complications of the flu

If you are having difficulty breathing, go to your nearest Emergency Department or call triple zero (000) for an ambulance.

Influenza infections can lead to serious complications, such as:

These complications are most likely in people at higher risk of severe illness.

Resources and support

Learn more about colds and flu.

Visit the Department of Health website for more information on the flu vaccine. You can also call the National Immunisation Information Line on 1800 671 811.

You can find out more about the National Immunisation Program on the Department of Health website.

If you are feeling concerned about any flu symptoms see your doctor. If you would like to speak to a registered nurse, call healthdirect on 1800 022 222, 24 hours a day, 7 days a week (known as NURSE-ON-CALL in Victoria).