A person is in intensive care with Legionnaires' disease after exposure to the bacteria from garden compost.
Canterbury Medical Officer of Health Dr Alistair Humphrey said the person was diagnosed two weeks ago and was recovering in Christchurch Hospital.
The doctor has issued a warning about the disease as warmer weather sees a spike in admissions because more people are gardening.
He urged gardeners to take care when opening bags of potting mix and compost to avoid a repeat of the high numbers who fell ill in spring 2017.
"Gardeners are at particularly high risk of catching Legionnaires' disease as the bacteria thrives in bags of potting mix and compost," he said.
Dr Humphrey says there were five simple actions gardeners should do to avoid getting Legionnaires':
• Open potting mix or compost carefully – use scissors instead of ripping the bag.
• Wear a well-fitting disposable face mask and gloves, and remember not to touch your mask when gardening.
• Reduce dust by dampening down potting mix or compost with a sprinkle of water.
• Work with potting mix or compost in a well-ventilated outdoor area.
• Thoroughly wash your hands after handling potting mix or compost.
Humphrey said several others had been admitted to hospital with the disease this year but did not require intensive care treatment.