Healthdirect Free Australian health advice you can count on.

Medical problem? Call 1800 022 222. If you need urgent medical help, call triple zero immediately

healthdirect Australia is a free service where you can talk to a nurse or doctor who can help you know what to do.

beginning of content

Influenza A

4-minute read

Key facts

  • Influenza A is a type of virus that causes the flu. Most people who have flu are infected with the influenza type A virus.
  • Symptoms of Influenza A include fever and chills, sneezing, coughing and a sore throat.
  • As well as infecting people, the influenza A virus can infect animals, including birds and pigs.

What is influenza A?

Influenza A is a type of virus that causes influenza (the flu), a highly contagious respiratory illness. If you get it, you will need to rest at home and avoid infecting others. Vaccination can protect you against influenza A.

The other types of influenza virus are type B and type C.

Influenza types A and B are the most common causes of flu in Australia and can cause major outbreaks and severe disease. Influenza type C can cause an illness in children that is similar to the common cold.

Most people who have flu are infected with the influenza type A virus. This virus has caused flu pandemics — the worldwide spread of a new disease. Influenza A has also caused most epidemics — the widespread occurrence of an infectious disease within a community at a particular time.

Although coronavirus (COVID-19), is a viral illness that has developed into a pandemic, the virus that causes COVID-19 is different from the one that causes influenza.

Both the influenza A and influenza B viruses circulate in the community and change continually, with new strains coming out each winter. This is why yearly vaccination is recommended.

What are the types of influenza A?

As well as infecting people, the influenza A virus can infect animals, including birds (causing avian flu) and pigs (causing swine flu). In some cases, these types of influenza can be passed on to humans.

Bird flu

Avian influenza — also known as 'bird flu' — is a subtype of influenza virus A (H5N1) that mainly affects birds. The virus has caused serious infections and even deaths in humans but has not been found in Australia.

Although bird flu can be severe, the number of cases found in humans has been small. Most people diagnosed with bird flu have caught it from infected birds — so far, there is no evidence that bird flu can pass from human to human.

Swine flu

Swine flu is a type of influenza A virus found in pigs. In 2009, a strain of flu virus known as H1N1 caused a respiratory infection in humans which spread rapidly around the world and became a pandemic. The World Health Organisation (WHO) declared the swine flu pandemic over in August 2010.

The 1918 flu pandemic was also caused by an influenza A H1N1 virus.

Swine flu is mild in most people but can be severe for some high risk groups such as people with chronic conditions, pregnant people and Aboriginal or Torres Strait Islander people.

Symptoms, treatment and prevention

If you have influenza A, you will have some or all of these symptoms:

Children may also have abdominal pain, nausea and vomiting.

In most cases you can treat the symptoms of a mild flu yourself by resting at home. Medicines are available to treat pain and fever. Most people will get better within 7 to 10 days.

The best way to prevent catching the flu is to have a flu vaccination every year, and to practise good hygiene.

For more information on treating flu symptoms, prevention and when to see a doctor, see Flu (influenza).

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

Is it a cold or the flu?

View this infographic to identify cold or flu symptoms and debunk the most common myths.

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

Last reviewed: April 2021

Back To Top

Need more information?

These trusted information partners have more on this topic.

Top results


Influenza, or 'flu', is in our community every winter. Getting a flu shot is the best way to protect yourself and your community from the flu.

Read more on NSW Health website

Avian Influenza (Bird Flu)

There are many types of influenza viruses that usually only infect birds; these are called avian influenza viruses. Some avian influenza viruses, such as H5N1 or H7N9, have been associated with human disease.

Read more on Queensland Health website

Influenza (the flu) - National Asthma Council Australia

What is Influenza? Influenza, commonly known as ‘the flu', is an illness caused when an influenza virus infects the respiratory tract – your nose and lung

Read more on National Asthma Council Australia website

Bird flu (avian influenza) -

Avian influenza, or bird flu, is an infectious disease caused by a type of influenza virus. Find out about outbreaks, symptoms, treatment and prevention.

Read more on myDr website

Influenza-65 years and over - Immunisation Coalition

Influenza can cause serious complications and hospitalisation for people 65 years and older. Because of this free influenza vaccine is available to people 65 years and older.

Read more on Immunisation Coalition website

2022 Seasonal Influenza Vaccines | Therapeutic Goods Administration (TGA)

2022 seasonal Influenza vaccines

Read more on TGA – Therapeutic Goods Administration website

Influenza and Travel - Immunisation Coalition

Don't spend your overseas adventure sick. Get all the tips, tricks and info you need to protect yourself from Influenza before you start your trip.

Read more on Immunisation Coalition website

Avian Influenza ("bird flu") fact sheet - Fact sheets

Avian influenza fact sheet.

Read more on NSW Health website

Bird flu (avian influenza) - Better Health Channel

The symptoms of bird flu in humans are similar to those of regular influenza.

Read more on Better Health Channel website

Influenza (flu) vaccine | Australian Government Department of Health and Aged Care

Information about influenza vaccines, who it is recommended for, how and where to get vaccinated. If you're eligible, you can get the influenza vaccine for free under the National Immunisation Program.

Read more on Department of Health and Aged Care website

Healthdirect 24hr 7 days a week hotline

24 hour health advice you can count on

1800 022 222

Government Accredited with over 140 information partners

We are a government-funded service, providing quality, approved health information and advice

Australian Government, health department logo ACT Government logo New South Wales government, health department logo Northen Territory Government logo Government of South Australia, health department logo Tasmanian government logo Victorian government logo Government of Western Australia, health department logo

Healthdirect Australia acknowledges the Traditional Owners of Country throughout Australia and their continuing connection to land, sea and community. We pay our respects to the Traditional Owners and to Elders both past and present.