This alert will no longer be updated daily. It will remain an active alert until the outbreak is stood down.
Key messages
- The Department of Health is investigating an outbreak of Legionnaires’ disease (legionellosis) with a significant increase in cases notified across metropolitan Melbourne and surrounding areas.
- There have been 113 confirmed and 5 suspected cases notified since Friday 26 July, mostly in adults aged over 40 years.
- Most cases have required hospitalisation, with a number of admissions to intensive care for severe community acquired pneumonia.
- Legionnaires’ disease can cause a chest infection with symptoms of fever, chills, cough, headache and muscle aches and pains. Other atypical symptoms may include nausea, vomiting, diarrhoea and confusion.
- All cases have visited or reside in metropolitan Melbourne. Those most at risk are adults aged over 40 years, especially people with other medical conditions or immune compromise, or who smoke.
- People who develop symptoms should seek urgent medical care.
- Healthcare professionals should have a high index of suspicion for Legionnaires’ disease in patients with compatible symptoms, particularly community acquired pneumonia with risk factors.
- If Legionnaires’ disease is suspected, request urgent urinary antigen testing through your normal pathology provider. As a priority, order Legionella culture and PCR (e.g. an ‘atypical pneumonia PCR’ panel) on sputum or other respiratory fluid samples (e.g. bronchial washings, endotracheal aspirates). Serology can be requested on blood at symptom onset and 3 to 6 weeks later as convalescent serology. Follow antibiotic guidelines or seek urgent advice from an infectious diseases specialist for choice of antibiotic.
- Legionnaires’ disease is an urgent notifiable condition that requires notification to the Department of Health upon initial diagnosis or clinical suspicion as soon as practicable by calling 1300 651 160 (24/7).
- Operators of cooling towers in the metropolitan Melbourne area are advised to ensure compliance with their cooling tower testing, servicing and auditing requirements.
What is the issue?
The Department of Health has identified an outbreak of Legionnaires’ disease (also known as legionellosis) with significant increase in the numbers of cases across multiple locations in metropolitan Melbourne since 26 July 2024.
The cooling tower identified as the source of this outbreak has been found. This tower was tested on 30 July 2024 and disinfected within 24 hours of that visit. While we are confident the source has been controlled, there may be some individuals who are yet to develop symptoms or who are already symptomatic but are yet to seek testing.
Test results indicate that the outbreak is caused by Legionella pneumophila serogroup 1, which can be detected through a Legionella urinary antigen test. This strain of Legionella is predominantly found in water systems and not in potting mixes.
Legionnaires’ disease is caused by Legionella bacteria which are widespread in the environment. Legionella is found in natural bodies of water such as rivers, lakes, creeks and hot springs. It is also found in spas, warm water systems and artificial systems that use water for cooling, heating or industrial processes such as cooling towers, as well as potting mix.
Who is at risk?
Although Legionella bacteria are commonly found in the environment, only a few people who come into contact with the bacteria become infected. In this outbreak, most cases are arising in people who are normally at greater risk of the infection, however, there are also cases in otherwise active and normally healthy adults.
People who are at greater risk of infection include those who:
- are aged over 40 years
- are smokers
- have a chronic lung disease
- have a weakened immune system
- have other underlying medical conditions such as chronic heart, liver or kidney disease, and diabetes.
Symptoms and transmission
Legionnaires’ disease usually presents as a chest infection with symptoms such as fever, chills, cough, headache and muscle aches and pains. Other atypical symptoms may include confusion, nausea, vomiting and diarrhoea. Some people with Legionnaires’ disease may also develop kidney impairment. Legionnaires’ disease can lead to serious illness and cases may require hospitalisation.
Legionnaires' disease is spread by breathing in fine droplets of water that contain Legionella bacteria. It is not commonly spread from person-to-person or by drinking contaminated water.
Recommendations
For the public
- People who live in, work in or have visited metropolitan Melbourne and surrounding areas prior to 31 July 2024, and develop symptoms of Legionnaires' disease, should seek urgent medical care.
For clinicians
- Consider Legionnaires’ disease in patients presenting with compatible symptoms who live in, work in or have visited metropolitan Melbourne and surrounding areas prior to 31 July 2024.
- If you suspect Legionnaires’ disease, request urgent urinary antigen testing through your normal pathology provider. As a priority, order Legionella culture and PCR (e.g. an ‘atypical pneumonia PCR’ panel) on sputum or other respiratory fluid samples (e.g. bronchial washings, endotracheal aspirates). Serology can be requested on blood at symptom onset and 3 to 6 weeks later (as convalescent serology)
- Early diagnosis and treatment with appropriate antibiotics are important. Refer to the current edition of the Therapeutic for treatment guidelines or consult with your local infectious diseases service.
- Legionnaires’ disease is an urgent notifiable condition that must be notified to the Department of Health upon initial diagnosis or clinical suspicion as soon as practicable and within 24 hours by calling 1300 651 160 and connecting to the relevant Local Public Health .
For cooling tower operators (in metropolitan Melbourne)
- Operators of cooling towers in the metropolitan Melbourne area are advised to ensure compliance with their cooling tower testing, servicing and auditing requirements.
Answers to common questions
