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Flu (influenza)

9-minute read

Key facts

  • Influenza (the flu) is a viral infection that causes symptoms like 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.
  • There is a vaccine available for the flu, and it’s recommended that everyone over the age of 6 months has a flu vaccination every year.
  • You can treat the symptoms of mild flu by resting and drinking plenty of water. Medicines are available to treat fever and aches.

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?

Influenza (the flu) is a viral infection affecting your nose, throat and sometimes your lungs.

What are the symptoms of the flu?

The symptoms of flu may include:

Cold and Flu Symptoms
This infographic helps you compare cold and flu symptoms.

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?

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 symptoms and:

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

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

Anyone who has cold or flu-like symptoms should see their doctor if they:

  • 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 their eyes
  • are worried

See fever in children and symptoms of serious illness in babies and children for other warning signs to look out for in small children.

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

What causes the flu?

Flu is caused by the type A, type B or rarely the 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.

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. This may be 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 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.

How is the flu diagnosed?

Your doctor may diagnose a probable influenza infection based on your symptoms alone. To help them do this, they may 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. They will most likely also do a test to rule out the possibility of you having COVID-19.

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

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.

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

Antibiotics only work on infections caused by bacteria. As the flu is caused by a virus, taking antibiotics will not help you get better faster or stop you from spreading it to other people.

Taking antibiotics can cause side effects like an upset stomach, diarrhoea and thrush. When you take antibiotics for the cold or flu, you also increase the risk of antibiotic resistance in the future.

Can the flu be prevented?

There is a vaccine available for the flu, and it’s recommended that everyone over the age of 6 months has a flu vaccination every year.

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.

For more information about the flu vaccine, see Flu Vaccine FAQs.

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.

Good hygiene is one of the best ways to help prevent colds and flu and to prevent them from spreading.

Resources and support

Learn more about colds and flu here.

If you are feeling concerned about any symptoms of a cold or flu then 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).

Visit the Department of Health website for more information on the flu vaccine or or call the National Immunisation Hotline on 1800 671 811.

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

Last reviewed: April 2022


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