Minimising the risk of Legionnaires' disease

The recent death of a Sydney woman in her 60s from Legionnaires’ disease prompted NSW Health to remind home gardeners to wear a face mask and gloves while handling potting mix and compost, and to wash their hands thoroughly, to avoid contracting the disease.

There were 96 cases of Legionnaires' disease so far this year from the type of bacteria that can be found in potting mix and soils in NSW, and 106 were reported last year, according to NSW Health.

NSW Health Executive Director Dr Jeremy McAnulty said, ''Most people who breathe in the bacteria don't become ill, but the risk of infection increases if you're older, a smoker or have a weakened immune system."

"Wetting the potting mix first also helps prevent any contaminated potting mix dust blowing up into the air and being inhaled.

"Even if you've been wearing gloves, make sure to wash your hands thoroughly with soap before eating or drinking as the bacteria could still be there," McAnulty said.

Symptoms of Legionnaires' disease can develop up to 10 days after exposure to the bacteria with symptoms including fever, chills, a cough, shortness of breath, aching muscles, headache, tiredness, loss of appetite and diarrhoea.

Legionella bacteria can multiply in bagged potting mix, mulch and other soil products. To minimise the risk, people should always read and follow the manufacturer's warnings on the outside of the bag.

Anna Ralph, Professor of Global and Tropical Health, Menzies School of Health Research, said the standard antibiotic treatment course given in hospital for pneumonia covers Legionella bacteria, curing the disease effectively. "But occasionally, especially if there is a delay, the infection can become very severe."

In Australia, the two species of Legionella that most commonly cause Legionnaire’s disease are Legionella pneumophila and Legionella longbeachae, said Dr Harriet Whiley, Associate Professor in Environmental Health at Flinders University.

L. pneumophila is found in engineered water systems such as cooling towers, spa baths, swimming pools and showers, whereas L. longbeachae is found in potting mix and soil, Whiley said.

"Legionnaires' disease is not transmitted person to person, but through inhalation or aspiration of the Legionella bacteria. This is why it is important to wear a mask, wet down soil and wear gloves/wash hands when handling potting mix," Whiley said.

Professor Elizabeth Hartland, who is Director and CEO of the Hudson Institute of Medical Research, noted that since Legionella is impossible to eradicate from the environment, people should take measures to protect themselves if undertaking a known risk activity such as gardening with potting mix.

If feeling unwell after handling potting mix, people should seek medical attention at the first sign of symptoms, Hartland suggested noting that standard diagnostic tests are not designed to detect Legionella longbeachae, so it's important to mention a risk activity like gardening with potting mix to medical practitioners for more specialised testing.

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