BARROW-IN-FURNESS, England -- Britain's worst outbreak of legionnaires' disease in a decade claimed its fourth victim Sunday, a woman aged over 70, AFP quoted public health officials as saying.

An 88-year-old man and two women in their 50s have also died since the outbreak -- traced to a 30-year-old air conditioning system at a local arts center -- began nearly three weeks ago.

There have also been 125 confirmed cases of the pneumonia-like illness, with more than 60 people in hospital undergoing treatment, said officials at Morecambe Bay Hospital in this city in Cumbria, northwest England. Local hospitals official Ian Cumming said late Sunday: "Furness General Hospital continues to see an improvement in the condition of the majority of the 40 cases remaining in hospital but, as this further death shows, we are by no means through this terrible time for the people of barrow."

Legionnaires' disease -- first discovered at an American legion convention in July 1976 where 29 people died -- causes high fever, dry cough, lung congestion and subsequent pneumonia.

It is commonly spread through contaminated air conditioners and ventilators, and is treated with antibiotics.