Image: Image (left) Pixabay. (Right): Representative image of a cooling tower. Photo: Tweed Shire Council.
The source of the largest outbreak of Legionnaires’ disease in Melbourne in two decades has been identified. A cooling tower in Laverton North in Melbourne’s West was the most likely source of the outbreak that led to the death of two people.
A woman in her 90s died from Legionnaires’ disease after she became ill and was hospitalised on July 30, 2024. A man in his 60s, who was hospitalised after he became ill on July 27, died on August 1.
Around 78 confirmed cases of Legionnaires’ disease and 10 suspected cases have been reported since the outbreak was first identified on Friday, July 26, 2024. The cases have been reported mostly in adults aged over 40 years. Most of the cases have required hospitalisation and some have been admitted to intensive care.
Cooling Tower Returns Positive Result
Earlier in the investigations, the health department had suspected that the current outbreak could have been from cooling towers, which are found in industrial complexes, workplaces and shopping malls. The health department said it had visited and disinfected cooling towers on 58 sites.
Chief health officer Clare Looker on Monday said that one of the cooling towers in Laverton North that had been tested and disinfected had returned a positive result for the Legionella bacteria. The exact location was not identified by the CHO.
Looker did not rule out multiple cooling towers as the possible sources of the outbreak and inspections were currently being carried out in Laverton North and Derrimut.
The disease is caused by Legionella bacteria which is widespread and found in natural bodies of water such as rivers, lakes, creeks, and hot springs. However, it can also be found in venues like spas, and artificial systems that use water for cooling or heating, including cooling towers.
Who Is At Risk?
Legionnaires’ disease is not normally spread from person to person or by drinking contaminated water. It is usually spread when a person breathes in fine droplets of water containing Legionella bacteria.
According to the health department, Legionnaires’ disease “usually presents as a chest infection with symptoms such as fever, chills, cough, headache, and muscle aches and pains.” Other symptoms may include confusion, nausea, vomiting, and diarrhoea, while some could develop kidney impairment. In some people, the disease can lead to severe illness that may require hospitalisation.
The health department said that all cases in the current outbreak had visited or resided in metropolitan Melbourne. “Those most at risk are adults aged over 40 years, especially people with other medical conditions or immunocompromised, or who smoke. People who develop symptoms should seek urgent medical care,” the CHO’s health alert said.
“Test results indicate that the outbreak is caused by Legionella pneumophila serogroup 1, which can be detected through a legionella urinary antigen test.” People most at risk of infection are those aged over 40 years, smokers, persons with a chronic lung disease, weakened immune system or have other underlying medical conditions such as chronic heart, liver or kidney disease, and diabetes.
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