Symptoms include fever, chills, muscle aches and pains, shortness of breath and coughing.
Anyone who develops such symptoms within two to 10 days after handling compost or potting mix should see their doctor without delay.
Legionnaires' disease can be a serious illness that requires hospital treatment.
The disease is more common in older people, smokers, people with underlying lung disease and other long-term conditions such as diabetes.
Dr Phil Shoemack, Medical Officer of Health for Toi Te Ora - Public Health Service, said young, fit and healthy people were rarely affected.
"The disease doesn't spread from person to person. Gardeners and farmers can take simple steps to reduce the risk of getting Legionnaires' disease," he said.
"When working with compost and potting mix it's important to take measures to avoid inhaling dust.
"For example, open potting mix and compost bags gently and away from your face, cut the bag open with scissors rather than ripping it, water gardens gently using low pressure and, where possible, avoid working in unventilated places such as closed sheds and greenhouses.
"When potting plants, gently wet the soil or compost first to reduce dust and wash your hands after handling soil or compost.
"Use of a face mask is recommended especially when these other measures are not practical or possible," Dr Shoemack said.
- For more information go to www.ttophs.govt.nz/legionellosis
