What you need to know about the flu

Influenza (flu) is a vaccine-preventable viral infection that can cause a fever, muscle aches, a headache, fatigue and a cough. Read on for a short history of the flu and some tips about what to do if you think you have it.

Flu – a short history

Flu is a contagious respiratory illness that has been affecting people worldwide for hundreds of years. While the flu is present every year as a seasonal virus, some years are worse than others. A well-known outbreak was the Spanish flu in 1918-19, which spread around the world as soldiers returned home at the end of World War I. Up to 100 million people died from the Spanish flu, which was significantly more than the 18 million who died in the war. It’s estimated that 15,000 Australians died during this period although as many as 4 in 10 people were infected. Indigenous Australians were severely affected, with a mortality rate approaching 50% in some communities. Scientists achieved a major milestone in 1933 when they discovered the virus that causes flu. Another milestone was the development of early flu vaccines in the 1930s and 1940s.

What causes influenza?

Flu is caused by the influenza virus. There are three different types of influenza virus with types A and B being the most common causes of flu in Australia, and most people who have flu are infected with type A. Both the A and B viruses circulate in the community and change continually, with new strains emerging each winter.

The change in strains is one of the reasons you should have a flu shot every year.

How flu spreads

People with flu can spread it to others in two main ways:

  • When an infected person coughs or sneezes, fine droplets are produced that can be breathed in by someone else.
  • Infected people can contaminate surfaces (for example, by touching them, or when droplets from their sneezes land on them) and another person who then touches the surface can become infected when they touch their mouth, nose, or eyes.

When are you most contagious with flu?

While you can infect others from the day before your symptoms start, adults are most likely to pass on the virus in the first 3-5 days of their illness and children can do so for a week or more.

Flu signs and symptoms will vary from person to person but typically might be:

Days 1-3:

  • Fever
  • Headache
  • Muscle pain and weakness
  • Dry cough
  • Sore throat
  • Blocked nose

Days 4-7:

  • A decrease in fever and muscle aches
  • A dry, sore or hoarse throat
  • Mild chest discomfort
  • Fatigue

Day 8 onwards

  • Symptoms decrease
  • Cough and tiredness can last 1-2 weeks or longer

Do I need to see a doctor for flu?

Most healthy people will recover on their own from the flu without needing to see a doctor, but you should seek medical help immediately if you have any of the following:

  • Any concerns about your health;
  • Difficulty breathing;
  • Chest pain;
  • Sudden dizziness;
  • Confusion;
  • Severe vomiting;
  • A rash and fever.

Children: You should take your child to a doctor if they have flu symptoms and a chronic medical condition, or if they experience signs of serious illness like poor feeding, dehydration or difficulty breathing, or if you are otherwise concerned about their illness.

At risk people: Anyone with a chronic medical condition, or who is otherwise “at-risk” should see a doctor immediately if they have flu-like symptoms (for a list of at-risk people, see Who is at risk of serious illness from the flu?).

How to avoid the flu

Here are five things you can do to reduce your chances of catching flu:

  • See your GP or pharmacist to discuss a flu shot every year. Even if you do get the flu, your symptoms may be milder if you are vaccinated.
  • Avoid contact with people who are sick.
  • Try not to touch your eyes, nose or mouth unless you have washed your hands.
  • Clean and disinfect surfaces if you are sharing space with someone who is sick.
  • Wash your hands regularly.


Flu has been infecting people around the world for centuries. Thanks to scientists, we now know about the different types of flu, how flu spreads and when we are most likely to pass it on to others. Talk to your GP or pharmacist about flu vaccines and how you can protect yourself against the flu.

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