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Legionella Guidelines

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Legionella

Legionella is a bacteria that is widely distributed in the environment. Legionella in its natural habitat interacts with other micro-organisms such as algae, amoebae and utilizes organic and inorganic nutrients.  It is found in fresh and brackish water, soil and in commercial potting mixes.  It grows optimally at around 35 degrees C.

Legionella may also be found in some artificial environments where water is present at temperatures favourable to growth in the form of biofilm which is a thin slimy layer where the water meets a surface such as an internal pipe wall.  This biofilm can break off and release legionella into the water circulation.  Such environments include circulating water in industrial cooling towers associated with air conditioning systems, refrigeration systems and water held at warm temperatures for bathing and showering.

If this water becomes aerosolised as droplets and inhaled by humans, the result may be legionnaires disease infection.  This may be very mild in some persons and very serious, even fatal in others.  Risk factors for serious disease include being elderly, sick, male, a heavy drinker or smoker or having an impaired immune system.  Although the term legionnaires disease is used for a particular type of infection by the legionella organism, a more general term for human infection is legionellosis.