What is the difference between bacterial and viral infections?

6-minute read

Key facts

Both bacteria and viruses can cause infections.
Because viral and bacterial infections can cause similar symptoms, it can be difficult to know what is causing your infection.
Antibiotics do not work for viral infections.
Similarly, antivirals do not cure infections caused by bacteria.

What is a bacterial infection?

A bacterial infection is an infection that’s caused by bacteria.

Bacteria are single cell organisms. They are so small that you can’t see them without magnification.

Your body is full of bacteria. In fact, it’s thought that your body has more bacteria than human cells. Most bacteria are harmless, and some are even helpful. The bacteria in your gut helps you to digest food.

Some examples of bacterial infections are:

What is a viral infection?

Like bacteria, viruses can cause infections.

Viruses are very small and live inside host cells. Viruses cause infections when they multiply inside your cells.

Viruses can be spread to other people by:

tiny droplets from your nose or mouth
vomit
faeces (poo)

Some examples of viral infections are:

How are bacterial and viral infections diagnosed?

It can sometimes be difficult to know what is causing an infection. This is because viral and bacterial infections can cause similar symptoms.

To see what sort of infection you have, your doctor will ask you about your symptoms. They may also examine you and may organise tests of your:

blood
urine (wee)
stool (poo)
swab from your nose or throat

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How are bacterial and viral infections treated?

It’s important to know if your infection is caused by bacteria or viruses. This is because the treatments differ.

Treating a bacterial infection

Doctors usually treat bacterial infections with antibiotics. It's important to use the right antibiotic for each type of bacterial infection. The right antibiotic will kill the bacteria or stop processes that they need to live and grow.

Antibiotic resistance is a growing problem in the world. It’s important that you take antibiotics exactly as your doctor or pharmacist tells you.

Your doctor will only prescribe antibiotics when they think the treatment will be of help.

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Treating a bacterial infection

Viral infections can’t be treated with antibiotics.

If you have a viral infection, your doctor may suggest:

resting at home to allow your immune system to fight the virus
staying hydrated by drinking water or rehydrating fluids or icy poles
pain-relief medicines, such as paracetamol and ibuprofen, to help with pain

Antiviral medicines can be used to treat some viral infections.

Notifiable disease and contact tracing

Some infections that are caused by bacteria or viruses are notifiable. This means that your doctor or the pathology service must tell the health authorities. This is to help control and stop the spread of infectious diseases.

Depending on your condition, you may be contacted by the health authorities. This is so that they can do contact tracing. Contact tracing helps them understand how you became sick and offer treatment to other people who may also be sick.

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Can bacterial and viral infections be prevented?

Many diseases that are caused by bacteria or viruses can be prevented by vaccination. These are known as vaccine-preventable diseases.

Many of these vaccinations are free through the National Immunisation Program Schedule.

Good hygiene practices can help to lower your chances of getting sick from bacteria or viruses. Good hygiene practices can also help lower your chance of spreading infections. You should:

wash your hands often
not share cups, drink bottles or cutlery
cough or sneeze into your elbow
use tissues and throw them in a bin as soon as you have used them

Resources and support

Learn which diseases are notifiable in Australia, on the Department of Health, Disability and Ageing website.

If you are worried that you have an infection, you can call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with 24 hours a day, 7 days a week.