People can catch the disease by inhaling airborne droplets or particles containing the pathogen.
Gardeners are at particularly high risk as the bacteria thrive in bags of potting mix and compost.
The illness may be mild but can sometimes be fatal.
It is more common in older people, particularly if they smoke, have poor immunity or a chronic illness.
However, sometimes even healthy young people have died from legionella pneumonia.
Symptoms can include dry coughing, high fever, chills, shortness of breath, muscle aches, headaches and diarrhoea.
If you have these symptoms, phone your general practice right away for advice and let them know if you have been handling potting mix or compost.
In 2019 there were 39 hospitalisations from legionnaires' in Canterbury, while data for hospitalisations in 2020 has not yet been released.
The Canterbury District Health Board is reminding gardeners of the five actions to avoid getting legionnaires:
• Wear a well-fitting disposable face mask and gloves before you begin gardening.
•Open potting mix or compost bags carefully by using scissors to cut off the top.
•Reduce dust by spraying some water into the bag.
•Work with compost in a well-ventilated outdoor area.
•Wash your hands thoroughly after handling potting mix and before touching your face or removing the mask.
- starnews.co.nz