Three people have died from the disease, an 81-year-old male, a 65-year-old male and a 58-year-old male, and a total of seven cases have been confirmed, spread between the Greater Glasgow and Clyde area and Lanarkshire.
Five of the cases were confirmed in the greater Glasgow and Clyde area and two in Lanarkshire.
Health chiefs say there is no great concern for any specific age group, however, they stress that the symptoms of the disease are common with other, mild ailments and are encouraging anyone showing these signs to visit their doctor.
Dr Syed Ahmed, NHSGGC lead consultant in public health, said: “Despite our very thorough investigations to date we have been unable to find a common source for the infections.
“We expect a small number of cases within the community every year but this rise, so close together, is most unusual and we feel we must treat these cases as an outbreak.
“The symptoms and signs of Legionnaires’ disease include headache, fever, dry cough, breathing difficulties, stomach pains and diarrhoea. I would like to advise anyone currently with these symptoms to contact NHS 24 on 08454 24 24 24 or to contact their own GP.”
The Public Health Protection Units from both NHS Greater Glasgow and Clyde (NHSGGC) and NHS Lanarkshire are working together in a joint investigation with Health Protection Scotland (HPS), the Health and Safety Executive, environmental health officers and other partner agencies in an attempt to establish the source of the outbreak.
Dr Ahmed added: “Together with NHS Lanarkshire, HPS, environmental health and other colleagues we are investigating each and every case to identify a common source.
“I would also like to stress that legionella cannot be spread from person to person.
“It is a bacteria found in water and can be spread through aerosols produced from water, such as air conditioning and showers and it cannot be contracted by drinking contaminated water.”