The worst outbreak of Legionnaires disease in Scotland’s history has been blamed on a network of industrial cooling towers in the south west of Edinburgh that have left one man dead and 12 critically ill in hospital.
Nicola Sturgeon, Scottish health secretary, told a press conference today that early indications suggested the source of the outbreak was a “contaminated cloud” emitted by one or more of the towers, which use the evaporation of water to cool industrial processes.
The toll had risen to 40 confirmed and suspected cases of infection with the bacterial lung infection today which carries a one-in-ten death rate.
The lethal bug is transmitted when infected water is inhaled as a vapour, and causes pneumonia-like symptoms. It does not spread from person to person.
As news of the outbreak spread, residents in the area took evasive action. One tweeted: “Legionnaire’s outbreak! Next to my house! Scared of going out.”
But Dr Duncan McCormick, consultant in public health medicine and chairman of the incident management team at NHS Lothian, said there was nothing to fear.
"There is no need to stay indoors. The main thing is to be aware of the risk to yourself, based on your other underlying conditions, and if you become unwell to contact your GP or NHS 24.
"Overall, I can assure people that you can go out of doors and, for the vast majority of the population, the risk is very low."
People living in the the Dalry, Gorgie and Saughton areas of the city were warned to be on the alert for symptoms including headaches, muscle pain, fever, chills and coughing up blood.
All 16 cooling towers in the affected area of the city have been disinfected with chlorine and other chemicals to kill the bacteria. But tests to confirm the source of the outbreak will take up to ten days.
Dr McCormick said the outbreak was “the largest cluster I have ever come across”. Edinburgh usually sees an average of five cases a year. The disease has an incubation period of up to 14 days and the first case in the current outbreak was diagnosed on May 28.
"If we are correct about the source being the cooling towers, we would expect to see people with symptoms present themselves over the next five or six days, followed by a decline. But we would expect an increase in the number before then," he said.
Those at highest risk are people over 50 with other health problems such as bronchitis or asthma. The man who died was in his 50s and had an underlying condition.
Two patients that had been "seriously unwell" had now been discharged, which was "really encouraging" indicating that the "treatment was working very well", Dr McCormick said.
Legionella bacteria are commonly found in sources of fresh water, such as rivers and lakes. Drinking water is not affected - the disease can only be caught from inhaling contaminated vapour. Air conditioning systems, showers, swimming pools and spas can pose a risk if they are not properly cleaned and maintained. Major outbreaks in Britain in the past have been linked with cooling towers.