Two people have recently been hospitalised in Hawke's Bay after contracting Legionnaires disease from water in their houses.

Two people in Hawke's Bay have contracted Legionnaires disease from water in their own homes with one so badly afflicted she has had her feet amputated.

Now the District Health Board is warning people against turning down their hot water cylinders to save money.

Hawke's Bay District Health Board's medical officer of health Nicholas Jones said the woman, aged in her forties, was admitted to Hawke's Bay Hospital on June 16 and is still in intensive care. The other victim, a man in his eighties, was admitted in late April and discharged in early May.

Tests on the water in both victims' homes found the presence of legionella bacteria, which can cause legionellosis, also known as Legionnaires' disease, which is a potentially fatal type of pneumonia.

It is contracted by inhaling water in the form of vapour or steam containing the bacteria.

Legionella bacteria can grow in water temperatures of 20-45degC. They thrive at tempertures of 32-44degC, but can't live at 60degC or higher.

Jones said the bacteria was found in the woman's hot water cylinder and in the man's water system, with his hot water cylinder a possible source.

He advised people to check their hot water cylinders were set to 60degC.

"We'd recommend you do not try to save money by turning your hot water cylinder temperature down because you will be running the risk of developing a severe illness in doing so," he said.

He said the woman had been unwell for about four days before being taken to hospital.

"The woman was admitted with very severe pneumonia then developed septic shock which resulted in problems with her organs and circulation to her feet and hands," he said.

"She was very, very, seriously ill and in a critical condition when admitted. She has made a lot of progress and the infection in the lung has improved considerably and she is now in a serious but stable condition," Jones said.

"What we know from our investigating officer is that the woman's husband does not like his hot water too hot, and the thermostat was observed to be below the recommended 60. It was set at about 52. We know the bacteria was growing in their hot water cylinder," he said.

The affected man, who lives in his own unit in a rest home complex, was not critically unwell when he was admitted, Jones said.

"We're still investigating the man's case. There was legionella in his water and we think the hot water cylinder is a possible source. The thermostat [on his cylinder] was set at the correct temperature. It might be that the thermostat was faulty. We haven't got to the bottom of that yet," Jones said.

LEGIONELLA