Key Points
- The Victorian Department of Health is investigating an outbreak of legionnaires' disease in Melbourne.
- There have been 33 confirmed and 10 suspected cases as of Tuesday afternoon.
- The disease can cause a chest infection with symptoms of fever, chills, cough, headache and muscle aches and pains.
Cooling towers across Melbourne are being disinfected in a bid to stem a growing outbreak of legionnaires' disease that has left several people in intensive care.
There are 33 confirmed cases and 10 suspected cases as of Tuesday afternoon but the number is expected to rise in coming days.
Six people were in intensive care on Monday.
The majority of patients admitted to hospital are male, aged over 50 and live or work in metropolitan Melbourne.
The source of the outbreak is yet to be confirmed and authorities are keeping an open mind, but Victorian chief health officer Dr Clare Looker believes it is likely to be a single cooling tower in Melbourne.
"We have some suburbs that have had more crossover of cases than others and these are really across the north and west of Melbourne," Looker said.
"At this stage, we haven't been able to identify a single site that has been visited by all the cases."
Eighteen cooling towers at public venues, industrial sites and factories were being disinfected and many patients had visited several of the sites.
Mapping software has been used to identify places the cases visited or passed by during their incubation period.
Melbourne residents are being urged to be vigilant about legionnaires' disease.
On Monday, Victoria's Department of Health issued an alert advising people who live in, work in or have visited metropolitan Melbourne and surrounding areas to be on alert for symptoms of the disease.
So, how do you know if you're at risk?
What is legionnaires' disease?
Legionnaires' disease is a type of pneumonia caused by a legionella bacterial infection of the lungs.
It is not commonly spread from person to person or by drinking contaminated water.
Richard Bentham, adjunct associate professor at Flinders University, said the legionella bacteria develops in warm water particles found in cooling towers or spa baths.
"Cooling towers are on many large buildings in cities … they produce a mist called drift that goes out of the top of the cooling tower and it carries the bacteria with them," Bentham told SBS News.
People can then be exposed to the legionella bacteria by contaminated water particles.
"If someone that is susceptible inhales that mist, and the mist can travel kilometres from the source, then they contract a pneumonia that can be quite serious."
What are the symptoms of legionnaires' disease?
Bentham said initial symptoms include a dry cough and tiredness, followed by a rapid fever.
People can experience muscle aches, headaches, tiredness, stomach aches and become sick with pneumonia, with a higher fatality rate in immunosuppressed patients.
Other atypical symptoms may include confusion, nausea, vomiting and diarrhoea.
Some people with legionnaires' disease may also develop kidney impairment.
Who's most 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.
Those most susceptible to the disease include people over 50 years, people with underlying lung or other serious conditions and smokers.
Bentham said the severity of illness depends on a person's ability to cope with disease but highlighted it was not contagious or transmitted via other people.
"If you start feeling unwell, you've got a dry cough, you're getting a bit of a fever, go to your physician straight away. The sooner you treat it, the better the outcome is," he said.
The best form of protection during the current outbreak is to wear masks to prevent breathing in contaminated water droplets and see your doctor for early prevention.
Symptoms typically occur between two and 10 days after exposure. The disease is treated with antibiotics, as the bacteria is resistant to penicillin.
How does it spread through potting mix?
Bentham, who consults on legionella risk management as associate director of Built Water Solutions, said a secondary type of legionella can be found in soil or potting mix.
In September last year, NSW Health warned gardeners to wear masks and gloves when handling potting mix, mulch or compost, after 54 cases were reported.
Legionnaires' disease can be spread through gardening soils, as well as pools, spas and water coolers. Source: Getty / Marcus Brandt
Washing your hands after handling the soil, especially before eating, drinking or smoking, is another way to reduce potential exposure.
With reporting from the Australian Associated Press.
