THE deadly legionella bacteria has been discovered at Edinburgh’s tram depot – less than a year after an outbreak across the city killed three men.
Traces of the pathogen were detected in a washing unit used to clean tram carriages at the Gogar terminal, sparking an immediate purge of the equipment.
The affected area was sterilised by independent water hygiene specialists and the council claims there was no risk to staff or members of the public at any time.
It is understood the legionella bacteria – which can grow into the fatal legionnaires’ disease – was found during routine tests last September as the tram depot was being commissioned for use.
The bacteria was first detected on September 27 in a washing unit separate to the main building and the area was given an “all-clear” certificate the following day.
Legionnaires’ disease is a potentially fatal form of pneumonia that struck down 101 Edinburgh residents in a major outbreak in Gorgie last summer. Investigations have been launched into the cause of the outbreak, believed to be centred on local cooling towers.
The disease, which is not contagious and cannot be spread directly from person to person, is caught by breathing in small droplets of contaminated water.
Expert Allen Wilson said warm temperatures and stagnant water created the conditions for legionella bacteria to occur. Around 500 incidents of detection are reported in the UK every year, he said.
“You need a few things for legionella to occur: water that’s been allowed to stagnate and needs to be at a temperature of between 20 and 40 degrees C. The closer it is to body temperature, the more it grows. It also needs some way to be converted into an aerosol droplet like you would get from shower heads.
“Something like a common pressure cleaner, like you might find at a washing unit, could create these respirable droplets.”
Jay Paisley, 49, one of the victims of last year’s outbreak, who spent three weeks in a coma recovering from the illness, said he was “shocked” to hear it had been detected again.
“There’s meant to be people out there monitoring the environment for this – we are all entitled not to be poisoned by corporate negligence. It’s down to people not cleaning stagnant water properly and it’s very concerning that this happened in Gogar because there is Roseburn Primary School nearby.”
A council spokesman said: “A very low count of legionella bacteria was detected in a washing unit in September and no staff or members of the public were at risk at any point.
“The area was treated and sterilised by independent water hygiene specialists immediately in a way that went over and above legal requirements. “The building continues to be monitored monthly and wash systems are flushed daily to maintain the highest safety standards.”
Assessing the risk
Legionnaires’ expert Allen Wilson explained that health authorities become aware of potential legionnaires’ outbreaks by medics reporting suspected cases rather than routine detections of legionella bacteria.
He said that if legionella is detected at a threshold less than 100 colony-forming units (CFU) – live bacteria that are able to multiply – of legionella per litre of water, it was deemed to require routine testing.
Between 100 and 1000 CFUs per litre, control measures should be reviewed alongside a risk assessment and samples retaken.
Where there is more than 1000 CFUs per litre of water, it should then be “shot dosed” with an appropriate biocide, as a precaution.
It is understood the bacteria found at Gogar measured 20 CFUs in a litre of water.