Investigations are under way to trace the source of an outbreak of Legionnaires\' disease which has left four people in hospital. NHS Lothian said four men, aged 39, 48, 60 and 63, were being treated in hospital after being confirmed as having the disease. Three are in intensive care, while another is being cared for in a high dependency unit. Four other people, two women, both aged 49, and two men, aged 88 and 63, are also suspected of having the illness. All of the cases have come from the south-west area of Edinburgh since May 7. The source of the outbreak is being investigated by officials from the City of Edinburgh Council\'s Environmental Health Department and the Health and Safety Executive, who are concentrating on the south-west Edinburgh area. NHS Lothian said steps are being taken to treat cooling towers in the area as a precaution until the source is located. Dona Milne, acting director of Public Health and Health Policy for NHS Lothian, said: \"We have four confirmed cases of Legionnaires disease which all seem to come from the same point source in the south west of Edinburgh. \"Anybody who develops symptoms of Legionnaires disease should contact NHS 24 immediately or go to their GP. The safety of the public is our number one priority and we would urge people to look out for the symptoms of this disease.\" The health board said Legionella bacteria is commonly found in sources of water, such as rivers and lakes. The bacteria can end up in artificial water supply systems, including air conditioning systems, water services and cooling towers. Symptoms include mild headaches, muscle pain, fever, a persistent cough and sometimes vomiting and diarrhoea. About half of those with Legionnaires\' disease will also experience changes to their mental state, such as confusion.