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Influenza A

5-minute read

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. The virus 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 or H1N1). 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 in humans and deaths but has not been found in Australia.

Swine flu: This is a type of influenza A virus found in pigs. In 2009, a strain of flu virus known as H1N1 caused the respiratory infection in humans that was commonly referred to as swine flu. It spread rapidly around the world and became a pandemic. The 1918 flu pandemic was also caused by an influenza A H1N1 virus.

What are the symptoms of influenza A?

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

Children may also have abdominal pain, nausea and vomiting.

Influenza A is a bit like a very bad cold, but a cold doesn't usually cause aches and pains or a high fever.

If your symptoms get worse instead of better, it's best to see a doctor. You should also get help straight away if you feel chest pain, you are short of breath, dizzy or confused, or you are vomiting a lot.

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

How is influenza A treated?

If you have influenza, you are likely to get better within a week or so by:

  • resting in bed
  • taking mild pain relief to reduce your pain
  • drinking plenty of liquids
  • eating light foods when you are hungry

In some people, the flu can be severe and lead to serious complications such as pneumonia. This is mostly likely to affect the very young, the elderly, pregnant women, Aboriginal and Torres Strait Islander people, and people with chronic health problems.

If this sounds like you, your doctor might give you antiviral treatment to reduce your symptoms and prevent complications. These treatments are most effective when started within 2 days of flu symptoms appearing, so it’s important to ask your doctor whether this type of treatment is right for you.

Antibiotics only work for bacterial infections, so they won't work for the flu, which is caused by viruses.

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

ASK YOUR DOCTOR — Preparing for an appointment? Use the Question Builder for general tips on what to ask your GP or specialist.

Can influenza A be prevented?

Influenza spreads very easily from one person to another. If you have influenza, you should stay at home while you're sick, cover your face when you sneeze or cough, and regularly wash your hands.

If you are around someone with influenza, you can help avoid getting sick yourself by regularly wiping surfaces they touch, using a cleaning cloth with detergent, and washing your hands.

Getting vaccinated each year before winter arrives is the best way to protect against influenza A. A new vaccine is needed every year because influenza viruses change constantly.

Flu vaccine is available for everyone aged over 6 months. The vaccine is particularly recommended if you are at risk of complications of influenza, or if you live or work with people at high risk of getting the flu.

Should I keep my child home from school?

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

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


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