Source of Vic's Legionnaires' disease outbreak found

Victorian health authorities say they have located and disinfected the source of the recent Legionnaires’ disease outbreak that has claimed two lives and hospitalised dozens more.

In an alert issued on 29 July, the Victorian Department of Health announced that it had identified an outbreak of Legionnaires’ disease with higher-than-expected numbers of cases across multiple locations in metropolitan Melbourne since 26 July. Usually presenting as a chest infection with symptoms such as fever, chills, cough, headache and muscle aches, Legionnaires’ disease can lead to serious illness requiring hospitalisation.

Legionnaires’ disease is spread by breathing in fine droplets of water that contain Legionella bacteria, which are found in natural bodies of water such as rivers, lakes, creeks and hot springs, as well as in spas, warm water systems and artificial systems that use water for cooling, as well as potting mix. Although Legionella are commonly found in the environment, only a few people who come into contact with the bacteria become infected.

In the recent outbreak, most cases have arisen in people who are at greater risk of infection — including those aged over 40 years, people with other medical conditions or immune compromise, and smokers — however, there are also cases in otherwise active and normally healthy adults. Most cases have required hospitalisation, with multiple admissions to intensive care for severe community acquired pneumonia. There have also been two deaths — a woman in her 90s and a man in his 60s, both of whom had been admitted to hospital.

Over the weekend, health authorities narrowed down the likely source of the outbreak to water cooling towers on industrial buildings in the Melbourne suburbs of Laverton North and Derrimut, with at least 54 towers in the area tested and treated to date. On Monday afternoon, Chief Health Officer Clare Looker revealed that testing on a cooling tower in Laverton North had returned a positive result for Legionella bacteria.

“I can confirm one of the towers we tested and which was subsequently disinfected earlier in our investigation has returned a positive Legionella sample,” Looker said. This provides confidence that the source of the outbreak has been identified and already treated, she stated; that said, testing in Laverton North and Derrimut will continue due to the large scale of the outbreak.

There have been 77 confirmed and seven suspected cases of the disease since 26 July, mostly in adults aged over 40 years. The number of confirmed cases has not increased since Sunday, with Looker saying this shows “a continued reduction in the number of cases being notified each day compared to last week” and suggesting that “we are now past the peak of the cases associated with this outbreak”.

That said, people who have lived in, worked in or visited Melbourne since mid-July are advised to seek medical advice if they have the symptoms of a chest infection alongside a fever, chill, cough and headaches.

Image credit: iStock.com/Gilnature