A male resident of a Greater Manchester nursing home is in intensive care after contracting Legionnaires' disease.
The Health Protection Agency (HPA) said the case at the Rose Court nursing home in Radcliffe was an isolated incident.
The man, who was taken to hospital on Monday, is being treated in Fairfield Hospital, Bury.
Initial tests show the source of the bacteria, which is transmitted through water vapour, did not come from water systems at the home.
"There is no evidence of any risk to the residents," said Dr Lorraine Lighton, a consultant in communicable disease control at the HPA in Greater Manchester.
She said investigations are continuing and the HPA will be monitoring the home as a precautionary measure over the next few weeks.