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Dr Ali Mohammadi said more people now realised the need to work with potting and compost materials in the open air, to wear a well-fitted mask and gloves and to wash hands afterwards.
People should enjoy gardening, but following simple safety practices could save them from "a potentially fatal pneumonia infection", he said.
Care should also be taken in opening bags of compost and potting mix-related products "as the microbes travel into the air through the dust".
Dr Mohammadi was born in Iran and undertook his legionnaire’s research through the University of Otago’s Christchurch campus.
Awareness about the disease had grown, but some people mistakenly thought the problem affected only the elderly, he said.
In a recent case, a Christchurch man in his early 40s had become very ill and had to be flown north for emergency treatment.
An Otago-led national study last year found a much higher-than-expected rate of legionnaire’s disease in New Zealand, and identified 238 cases requiring hospitalisation in the year to May 20, 2016.
Fifteen people had died within 90 days of their illness being diagnosed.
In 2019, 20 disease cases were notified in Otago-Southland, and two people died, one in Dunedin and the other in Central Otago.
There have since been several more such deaths in Otago-Southland.
The university’s Christchurch campus was one of the world’s leading centres for legionnaire’s disease research, he said.
Dr Mohammadi graduated from Otago last month with a PhD, based on his study of this disease.
His research focused on developing detection methods for Legionella longbeachae — the organism responsible for most legionnaire’s disease in New Zealand — in clinical and environmental samples.
He remained optimistic that a breath test would eventually developed which would provide a swifter and less intrusive test for the disease.
Two of his doctoral supervisors, Dr Amy Scott-Thomas and Prof Steve Chambers, were still working on the development of such a breath test, he said.
Dr Scott-Thomas said such a breath test could soon be developed, subject to research funding.
Legionnaires’ disease was under-diagnosed in patients admitted to hospital as many could not to produce a sputum sample for microbiological testing.
However, everyone could easily produce a breath test sample.
If such a test was developed the clinical team could gain a definitive diagnosis quickly and "allow fast and effective treatment with the correct antimicrobial therapy", she said.