Legionnaire's disease got its name in a blaze of publicity when attendees at the 1976 Philadelphia State Convention of the American Legion were struck down with severe pneumonia. They had stayed at the Bellevue-Stratford Hotel from 21 to 24 June: 182 fell ill and 29 died; 39 passers-by were also affected, five fatally. Funerals and marching legionnaires made good television. The story was top of the news for five nights. But the cause was a mystery until a cold review of samples from victims was conducted six months later. It turned out to be a bacterium. This was unexpected. The pathology didn’t fit a bacterial cause, and it was widely believed that bacteria did not spread on the wind.

The first recorded Scottish outbreak was in 1973, with 89 cases and three deaths. The sufferers were mostly from Glasgow. They had been on a package holiday to Benidorm. The lead Scottish investigator ruled out all known causes and was decorated by the Franco government for exonerating Spain. A look-back using tests developed after the discovery of Legionella revealed the actual cause. In 2012 hotels in Benidorm are still infecting tourists with Legionella.

The first case in the current Edinburgh outbreak came to light on Monday 28 May. By Sunday 3 June there were eight cases. Foreign travel was soon ruled out as a common factor. Cooling towers became prime suspects. They are often the source in community outbreaks: the organism grows well in the slime that builds up if maintenance is poor, and they pump out aerosols that travel on the wind. The location of victims pointed to Gorgie, Dalry and Saughton, areas to the south-west of the city centre. The 16 cooling towers there were blasted with chlorine-based biocide.

Because the incubation period can be up to two weeks, a continued rise in the number of cases was predicted. On Tuesday 5 June there were 32, on Wednesday 40, on Thursday 61, on Friday 74 and on Saturday 80. The death of Robert Air was reported on Wednesday; he had been working on a building site in Gorgie.

Identifying which cooling tower caused the outbreak will not be easy. The numerical modelling of atmospheric dispersion is well developed. But the mathematics is complex and uncertain. Do you use Lagrangian, Gaussian or Eulerian models? Predicting air flow over the sea is much easier than in towns: stand close to a tall building on a windy day and you’ll feel why. An air flow fit would be helped a lot by finding Legionella bacteria in a tower with the same molecular fingerprint as bacteria from cases. They are being looked for.

The Scottish health minister, Nicola Sturgeon, has dominated media coverage of the outbreak. She has also made use of SGoRR, the Scottish Government Resilience Room, based on COBR, the Cabinet Office Briefing Rooms in Downing Street. It is very hard to justify the involvement of SGoRR. The incident team dealing with the outbreak appears to be doing an effective job. It should be left to get on with it.

Cooling tower problems have been identified in two businesses in Wheatfield Road. It runs into the Gorgie Road, where Robert Air had been working. One is the North British Distillery. The other is Macfarlan Smith, a pharmaceutical company which produces alkaloid opiates and its own speciality, Bitrex, the bitterest substance known. It is put into many things including alcohols, pesticides, shampoos, moth balls, toilet cleaners, disinfectants and air fresheners to make them unpalatable. No smoking guns yet, just improvement notices to both firms from the Health and Safety Executive. But it would be embarrassing if a business engaged in making disinfectants turned out to have endangered the public because it had failed to use them.