There have been 10 confirmed cases of Legionnaires disease in Christchurch over the past week, and 21 cases since October.
Canterbury has the country's highest rates of the potentially-fatal Legionnaires disease, while New Zealand has the highest reported cases of the disease in the world.
Gardeners are being warned to take precautions, as compost and potting mix is the main contributor to contracting the disease.
"Reducing the risk of becoming infected is vital as more of us get out into our gardens with the longer days and warmer weather," says Canterbury Medical Officer of Health, Dr Ramon Pink.
In the last 12 months, 271 cases have been nationwide, 49 of those in Canterbury.
Of the patients that are hospitalised with the disease, 30 per cent are admitted to the intensive case unit.
* Dry coughing
* High fever and chills
* Diarrhoea and/or vomiting
* Shortness of breath
* Chest pains
* Abdominal pain