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Disease groups:
At a glance
- No vaccine available – read more about prevention
- Nationally notifiable disease
About legionellosis
Legionellosis is any disease caused by Legionella bacteria.
There are 2 types of Legionella bacteria that commonly cause disease in Australia.
Legionella pneumophila is found in warm water. It is most often associated with water systems such as:
- air-conditioning cooling towers
- whirlpool spas
- showers
- decorative fountains
- car washes
- water misters.
Legionella longbeachae is found in soil. It is most often associated with:
- potting mix
- compost
- garden soil.
Why it matters to public health
Legionella bacteria live in water and soil. The bacteria don’t usually cause disease, but they can when people breathe them in.
Legionellosis is uncommon in Australia. About 400 cases are notified each year, mostly in older people and those that are immunocompromised.
But it can cause severe disease and death.
Outbreaks of legionellosis can occur when many people are exposed to a contaminated source, such as an air conditioning cooling tower that contains the bacteria.
Because of these major impacts, we:
- monitor and report on legionellosis in Australia
- plan for how to manage outbreaks.
Symptoms
If you’re looking for advice about your own health or treatment options, see healthdirect or speak with a qualified healthcare professional. Our role is to provide public health advice – information and guidance that helps prevent disease, protect communities and improve wellbeing at a population level.
Infection with Legionella bacteria can cause mild to severe disease.
Mild disease is known as Pontiac fever.
Severe disease is known as Legionnaires’ disease, a severe form of pneumonia.
Pontiac fever
Symptoms can include:
Legionnaires’ disease
Symptoms can include:
- fever and chills
- cough
- shortness of breath
- muscle aches
- headaches
- fatigue
- loss of appetite
- diarrhoea
- vomiting.
Legionnaires’ disease can cause severe pneumonia, organ failure and sometimes death.
Read more about the symptoms, diagnosis and treatment of legionellosis.
healthdirect’s symptom checker can help you decide whether to see a health professional.
Onset of symptoms
Pontiac fever
Symptoms of Pontiac fever usually start between 4 hours and 3 days after getting infected.
Legionnaires’ disease
Symptoms of Legionnaires’ disease usually start between 2 and 10 days after getting infected.
How it spreads
Legionella pneumophilia can infect people when they breathe in contaminated airborne particles. These most commonly come from built water systems, such as cooling towers and showers.
Legionella longbeachae can infect people when they breathe in dust from contaminated potting mixes.
Infectious period
Legionellosis does not usually spread between people.
Prevention
Building owners and managers must comply with legislative requirements to reduce the growth of Legionella pneumophila in cooling water systems and warm water sources.
The best ways to protect against Legionella longbeachae are to:
- always follow manufacturers’ warning labels on garden products
- wear a mask and gloves when handling potting mix, compost and garden soil
- open bags of potting mix, compost and soil products with scissors and do it outdoors, in a well-ventilated area
- wet soil products before handling them to minimise dust
- wash your hands after gardening or handling potting mix, compost or soil products.
Read more ways to prevent legionellosis.
Priority groups and settings
Some people are at greater risk of getting legionellosis or getting very sick from it.
People at greater risk should take steps to protect themselves.
People at greater risk of severe disease
Legionellosis poses a greater risk of severe illness for people who:
- are aged 50 years or older
- are immunocompromised
- smoke
- have certain medical conditions, such as
People at greater risk of exposure
Anyone could be exposed to Legionella bacteria.
People who are around a device that produces aerosols – like a cooling tower or an air conditioner – that is contaminated with the bacteria can be exposed to Legionella pneumophila.
People who use potting mix, mulches, composts or garden soils are at greater risk of being exposed to Legionella longbeachae.
Diagnosis and treatment
A healthcare professional can diagnose legionellosis through a:
- blood test
- urine test
- sputum (phlegm) test.
Sometimes a specimen from the lower respiratory tract is required.
You can use healthdirect’s directory to find a health service near you.
Most people who have Pontiac fever recover without needing any specific treatment.
People who have Legionnaires’ disease are treated with antibiotics, and might need to be cared for in hospital.
Read more about how to manage or treat legionellosis.
Surveillance and reporting
Legionellosis is a nationally notifiable disease – these are diseases that present a risk to public health.
Health authorities in each state and territory report new confirmed and probable cases to us daily through the National Notifiable Diseases Surveillance System.
This is part of our surveillance activities, which help us monitor case numbers around the country and understand disease patterns.
We analyse the data and report on case numbers and other data through our data visualisation tool, where you can filter and search the latest information.
Outbreaks
Legionellosis outbreak investigations are focused on:
- finding the likely source of infection
- preventing further spread.
For Legionella pneumophila, outbreak investigations usually focus on exposure to:
- cooling towers
- air-conditioning systems
- warm water systems (or water distribution systems)
- spa pools.
Control measures for Legionella pneumophila might include:
- disinfecting the source
- issuing alerts to encourage people with symptoms to seek medical care
- alerting healthcare professionals to consider legionellosis in their patients with relevant symptoms
- giving feedback to building owners and relevant authorities.
For Legionella longbeachae, outbreak investigations usually focus on exposure to:
- potting mix
- compost
- soil products.
Public health authorities might put out alerts to inform people about the risk and provide prevention advice.
Read more about how the Australian Government defines and plans for outbreaks.
Support
For information about legionellosis in your state or territory, see:
- Australian Capital Territory
- New South Wales
- Northern Territory
- Queensland
- South Australia
- Tasmania
- Victoria
- Western Australia.
If you need mental health support, see a list of organisations, websites and services that offer support, counselling and information.