Legionnaires' fear as woman dies in south Wales
A 64-year-old woman has died of suspected Legionnaires' disease in south Wales.
Another 13 people are being treated for the disease and 11 of the cases are said to be linked.
Health officials said the outbreak is clustered around the Heads of the Valleys corridor.
Public Health Wales (PHW), the Health and Safety Executive and environmental health officers from seven council areas are investigating.
The woman died in hospital on Monday, said Public Health Wales.
"We have 14 cases of Legionnaires' disease," said a spokeswoman for PHW. "At present 11 can be linked together as an outbreak.
"The other three we cannot yet say for definite that they have anything in common with the 11, but we are continuing to investigate."
Investigations into the possible source of the outbreak were ongoing.
Information had been circulated advising GPs of the steps to be taken if patients report symptoms.
Dr Gwen Lowe, Public Health Wales consultant in communicable disease control, said Legionnaires' disease was a rare but potentially life-threatening illness.
"Most cases are isolated but outbreaks can occur," she said.
"People become infected when they inhale bacteria spread through the air in the form of a fine mist or droplets from a contaminated water source.
"The disease cannot be passed from person to person."
Legionnaires' disease begins with flu-like symptoms and can lead to pneumonia, usually in adults, she added.
Anyone worried about their health should contact their GP.
The councils involved in the investigation include Cardiff, Merthyr Tydfil, Rhondda Cynon Taf, Caerphilly, Blaenau Gwent, Torfaen and Monmouthshire.
The outbreak control team, which also includes representatives from Cwm Taf Health Board, Aneurin Bevan Health Board, and Cardiff and Vale University Health Board, will continue to monitor the situation closely.