Australia: Melbourne Legionnaires’ disease outbreak affects dozens
The Victoria 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.
To date, there have been 77 confirmed and 7 suspected cases notified since Friday, 26 July, mostly in adults aged over 40 years. All cases have visited or reside in metropolitan Melbourne.
Most cases have required hospitalization, with multiple admissions to intensive care for severe community acquired pneumonia.
Health authorities say investigations and control measures are underway to identify the source of the outbreak through testing and disinfecting of local cooling towers primarily in the Derrimut and North Laverton area. To date, 54 sites with cooling towers have been treated, with more in the coming days.
Test results indicate that the outbreak is caused by Legionella pneumophilia serogroup 1, which can be detected through a legionella urinary antigen test.
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.
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.
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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.