Sources of Legionellosis

The bacteria responsible for infections such as Legionnaires’ disease occur naturally at low levels in mud, soil and surface water courses. It is when the bacteria enter man made water systems that they find the optimum conditions for growth. These conditions include:

• Temperature range of 20-45oC
• The presence of nutrients such as rust, sludge, bio-films and organic materials such as those found in old seals and gasket materials

Although the bacteria thrive in the 20-45oC range they have been found in water temperatures as low as 6oC. Below 20oC and the bacteria becomes dormant and they cannot survive in temperatures above 60oC.

The following systems have been associated with outbreaks of Legionellosis:

• Cooling towers
• Air conditioning/heating and ventilation units
• Industrial air scrubbers
• Commercial and domestic hot and cold water systems
• Showers
• Spa pools
• Ornamental water features
• Coolant for engineering cutting equipment
• Greenhouse watering, irrigation or misting systems
• Gardening compost