The bacteria that causes Legionnaires’ disease thrives in fresh water. Image source: Janice Haney Carr, via Wikimedia Commons
An outbreak of Legionnaires’ disease has been reported in Victoria, with an elderly woman confirmed dead from the disease.
There are at least 60 confirmed cases of the disease, which authorities believe originated in water cooling towers in Melbourne’s west.
It is the biggest outbreak of Legionnaires’ disease in Victoria since 2000, when 125 cases were reported at Melbourne Aquarium.
Authorities believe it likely that the origin point was at one of over 100 towers on industrial buildings across Laverton North and Derrimut. Authorities have begun inspections and disinfections of all the potential sites.
Chief Health Officer Dr Clare Looker has stated that there was a “high probability” the source of the outbreak had already been neutralised through disinfection.
Looker’s statement was “driven by some pretty compelling epidemiology and crossover of where many of our cases have visited”.
“I’m cautious — I obviously can’t say that with certainty — until we have test results back.”
Most of the reported cases are currently in hospital for treatment. A woman in her 90s died in hospital from the disease, after becoming unwell on Tuesday.
Legionnaires’ disease is caused by any species of Legionella bacteria, which is found naturally in fresh water. It can contaminate natural sources, such as lakes or hot springs, or artificial sources of water, such as hot tubs, water tanks, or water cooling systems.
The disease is not contagious and does not spread through direct person-to-person contact.
It instead spreads through water particles that contain the bacteria, which can be aerosolised and inhaled. Most individuals exposed will not become infected.
The bacteria have an incubation period of 2-10 days, with rare cases of incubation extending to as long as 20 days, after which symptoms occur.
Prevention of Legionella often involves keeping water sources above or below the bacteria’s preferred temperature range of 20–55 °C, preventing stagnation, preventing biofilm development, and periodic disinfections of water systems.
Symptoms often present similarly to a chest infection, but can include fever, chill, headaches, cough, muscle pains, nausea, vomiting, diarrhoea, and confusion.
There is no vaccine available, with the disease instead treated with specific antibiotics.
Victorian authorities encourage people who have visited Melbourne since mid-July and present these symptoms to seek medical aid.
Due to the bacteria’s incubation period, it is possible that case numbers may rise in Victoria.
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