Legionella pneumonia from a novel industrial aerosol.

After a worker from a plastics factory was diagnosed with legionella pneumonia it was learnt that a retired employee at the factory had been in hospital with a serious chest infection six months before and legionella pneumonia was diagnosed in retrospect from stored serum. The likeliest common source was a machine cooling system that took water from an uncovered water tank outdoors (from which Legionella pneumophila was isolated) and which generated an aerosol through a crack in the flow meter sight glass.