A surge in the number of deadly Legionnaires' disease cases has health authorities worried.
The disease killed top chef Ross Burden in July and there were ten cases during October and November at Christchurch Hospital.
Mr Burden, 45, was a popular television personality in New Zealand and the United Kingdom, where he worked with top chef Ainsley Harriott.
Mr Burden's mother Jude Harwood has laid a complaint after her son died at Auckland Hospital, Fairfax reported today.
The chef was previously reported to have died of cancer. He was receiving treatment for leukaemia, although there was social media chatter in July that Legionnaires' killed him.
Mr Burden had breathed in Legionella bacteria present in Auckland Hospital's hot water system, according to an interim coroner's report the Sunday Star-Times cited.
The disease is a severe form of pneumonia.
Nine of the Christchurch patients said they were gardening or exposed to compost or potting mix before contracting the illness.
Canterbury District Health Board described the ten cases as a "surge" and warned the Legionella bacterium was commonly found in soil, potting mix or compost.
"It thrives in warm, moist conditions and becomes dangerous when dust or droplets from one of these products infected with Legionella bacteria is inhaled. It can then cause a severe, even fatal disease," the health board said.
Dr Alistair Humphrey, Canterbury Medical Officer of Health, warned people ahead of what could be a busy, and "potentially risky" weekend in the garden.
"It is important gardeners follow five simple steps to avoid catching Legionnaires' disease from potting mix or compost," Dr Humphrey said.
The first step was to open potting mix bags carefully using scissors, rather than by ripping them.
The second step involved people wearing disposable face masks and gloves, and opening bags away from their face.
The next steps were doing potting in well-ventilated outdoor areas, and dampening the potting mix or compost with a sprinkle of water to reduce airborne dust.
Dr Humphrey said the final step was to wash hands thoroughly after gardening or handling potting mix.
Anyone could catch Legionnaire's but people over 50 years old, those with a long-term illness, especially lung disease, people with low immunity, and smokers were most vulnerable.
Symptoms included dry coughing, high fever, chills, diarrhoea, shortness of breath, chest pains, headaches, excessive sweating, nausea, vomiting and abdominal pain.
The Canterbury District Health Board said anyone experiencing these symptoms should see their doctor immediately, and tell them if they had been handling potting mix or compost.