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Flu (influenza)

8-minute read


Flu symptoms can be very similar to the symptoms of COVID-19. Even if your symptoms are mild, get tested for COVID-19 immediately — use the colds and flu Symptom Checker if you're not sure what to do.

What is the flu?

The flu is a viral infection affecting your nose, throat and sometimes your lungs. Typical symptoms of flu include fever, sore throat, tiredness and muscle aches.

What are the symptoms of the flu?

The symptoms of influenza (flu) may include:

Cold vs flu
See the full Is it a cold or the flu? infographic.

See your doctor if you have cold or flu-like symptoms and:

  • can’t or won’t drink fluids
  • are vomiting frequently and/or are unable to drink fluids
  • have an intense headache
  • are pale and feel sleepy
  • have chest pain
  • are experiencing breathing difficulties
  • develop a rash with fever
  • are experiencing neck stiffness
  • find light hurts your eyes
  • you are worried

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

When should I see my doctor?

See your doctor if your child has cold and flu symptoms and has a chronic medical condition. Warning signs of severe illness including poor feeding, dehydration and difficulty breathing.

See fever in children and symptoms of serious illness in babies and children for more information.

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

What causes the flu?

Flu (influenza) is caused by the type A, type B or the rarely type C influenza virus. Only types A and B cause major outbreaks and severe disease, while type C can cause an illness in children similar to the common cold.

Most people get infected with the influenza type A virus. This virus has caused flu pandemics (the worldwide spread of a new disease) and most epidemics (the widespread occurrence of an infectious disease in a community at a particular time).

You can catch flu all year round, but it is especially common in winter. In this case, it is called 'seasonal flu'. Influenza type A viruses are found in many animal species although water birds are their natural host. Types of influenza A viruses you may have heard of include avian (bird) flu and H1N1 (swine) flu. The influenza type B virus is mostly a human disease.

How is the flu diagnosed?

If you are otherwise fit and healthy, there is usually no need to see a doctor if you have flu-like symptoms. But you should see your doctor if you or your child have flu-like symptoms and any of the following apply to you:

  • You are younger than 5 years old
  • You are aged 65 years or older and living in an aged care home
  • You have heart or kidney disease, or a medical condition like type 2 diabetes
  • You're pregnant
  • You are very obese (you have a Body Mass Index [BMI] of 35 or higher)
  • You are an Aboriginal or Torres Strait Islander person
  • You have severe asthma, breathing problems or a lung disease (e.g. cystic fibrosis)
  • You have a disease that affects your muscles and/or the nerves that control them, and that can affect your ability to breathe (e.g. muscular dystrophy)
  • You have a weakened immune system (e.g. people with HIV, people taking medicines to suppress their immune system)
  • You are homeless
  • You are a smoker

This is because flu can be serious for you and your doctor may want to prescribe antiviral medication.

Your doctor may diagnose a probable influenza infection based on your symptoms alone. To help them do this, they will listen to your chest using a stethoscope.

If your doctor wants to be sure of the diagnosis they may take a sample of cells and mucus from your nose or throat using a sterile cotton swab. This sample will be sent to a pathology laboratory for testing.

How is the flu treated?

In most cases you can treat the symptoms of a mild flu yourself. Most people will get better by themselves within 7 to 10 days and without any treatment.

Some things you can do to relieve flu symptoms include:

  • getting plenty of rest
  • drinking plenty of water and other non-alcoholic fluids to prevent dehydration
  • keeping warm
  • eating a healthy diet with plenty of fruit and vegetables
  • avoiding exposure to cigarette smoke if possible
  • inhaling steam from a hot bath or shower in a closed room to help relieve a blocked nose - remember to always directly supervise children near hot water

If you have a sore throat try:

  • gargling with warm salty water
  • sucking on an ice cube, ice block or a throat lozenge
  • drinking hot water with honey and freshly squeezed lemon juice

There are also several medicines available to ease cold and flu symptoms, such as pain and fever.

Can the flu be prevented?

There is a vaccine available for the flu and it's recommended 'at risk' people, such as the elderly or those with chronic illnesses, should have an annual flu vaccination. Free flu vaccinations are also available for children aged 6 months to 5 years.

Flu viruses circulating in the community continually change, and the immunity provided by the vaccine doesn’t last a long time. That's why yearly vaccination is recommended.

Other ways to help prevent flu include antiviral medicines, although these are only recommended for preventing flu if you have been exposed to the flu in the previous 48 hours.

Antibiotics only work for bacterial infections so they won't work for colds and flu which are caused by viruses.

Colds and flu are very contagious viral infections and you can catch a cold or flu at any time of the year, not just in winter. However they are more common during the winter months, possibly because people are more likely to stay indoors and be in close contact with each other.

If you have a cold or flu and you sneeze or cough, tiny droplets of fluid containing the virus are launched into the air. These droplets spread about 1 metre and are suspended in the air for a while so they can be breathed in by someone else who may then become infected.

These tiny droplets of fluid can also land on surfaces. Anyone who touches these surfaces can also catch a cold or flu if they pick up the virus on their hands and then touch their nose or mouth.

If you have a cold or flu and you touch your mouth or nose and then touch a person or object without first washing your hands, then you can transfer the virus to that person or object. Good hygiene is one of the most important ways to help prevent colds and flu and to prevent them from spreading.

Everyday items at home and in public places can easily become contaminated with traces of these viruses including food, door handles, remote controls, handrails, telephone handsets and computer keyboards.

What should I know about the flu vaccine?

The flu vaccine is available to anyone from 6 months of age, and is free for children aged 6 months to less than 5 years. The best time to get the flu shot is early autumn to allow time for your immunity to be strengthened before the flu season (June to September) starts. It is important to have the vaccine each year to continue to be protected because your immunity decreases over time and the flu strains change over time as well.

The flu vaccine is also free for the following people:

  • anyone aged 65 years and over
  • all Aboriginal and Torres Strait Islander people aged 6 months and over
  • pregnant women
  • anyone over 6 months of age with medical conditions such as severe asthma, lung disease or heart disease, low immunity or diabetes that can lead to complications from influenza

There is a range of flu vaccines available in Australia, some of which are provided by the National Immunisation Program.

Most people have a vaccination that covers 4 strains of influenza. Learn more about the flu vaccine.

You should wait at least 7 days between your flu vaccination and any COVID-19 vaccinations. Speak to your doctor for more information.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: June 2021

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