One person is dead and four others have fallen ill in a recent spate of cases of Legionnaires' Disease, with health authorities pointing the finger of blame at a humble gardening product.

The person who died is believed to have contracted the illness overseas, while four others in Canterbury are thought to have become infected since September through contact with potting mix.

Legionnaires' Disease is a pneumonia caused by Legionella bacteria that are commonly found in water and soils, including potting mix and compost.

Symptoms of the disease may include dry coughing, high fever, chills, diarrhoea, shortness of breath, chest pains, headaches, excessive sweating, nausea, vomiting, and abdominal pain. In some cases it can lead to death. Older people and those with long-term illnesses are most at risk.

Dr Ramon Pink, Medical Officer of Health for Canterbury, said recommendations for handling and warnings were printed on most bags of potting mix.

"It is very important to take care to avoid inhaling the dust when opening and handling the potting mix. Bags should be carefully opened in a well-ventilated area, preferably outdoors, and away from the face."

"Dampening down the mix with gentle watering is advised. Also make sure that you always wash your hands after handling potting mix and doing any gardening."

In the past 12 months, 15 cases of Legionellosis had been notified in Canterbury. Nationally in 2008 there were 76 cases notified, including four deaths.

In 2005, three people in Canterbury died and at least 20 others fell ill in a Legionnaires' outbreak.