Investigation and control of a cluster of cases of Legionnaires disease in western Sydney.

Three cases of Legionella pneumophila infection were identified in Sydney's west in November 1998. Epidemiological investigations identified an association with one workplace. Environmental sampling revealed that the cooling towers in the workplace, and at 2 other premises within a 1 km radius of the workplace, were positive for L. pneumophila serogroup 1 (LP1) which was indistinguishable from clinical isolates of 2 of the cases on DNA fingerprinting. Our report highlights limitations of the current control program for Legionella in cooling towers, including the finding of unregistered cooling towers, cooling towers positive for LP1 despite satisfactory results on inspection, and cooling towers potentially linked to disease with counts of LP1 below the current protocol requirements for immediate decontamination.