Legionella disease

Legionella Disease (also known as Legionnaires Disease or Pontiac Fever) is a respiratory illness caused by the legionella bacteria which occurs naturally in the environment such as soils, composts, potting mixes, air conditioning systems and water storage tanks. The disease is more common in older people, smokers, chronic disease sufferers and those with weaker immune systems. Doctors are legally required to notify the Public Health Service of cases of Legionella  disease under the Health Act 1956

About 50 different strains of Legionella bacteria are known. One strain of bacteria called Legionella pneumophilla has been responsible for illnesses linked to some types of air conditioning systems in buildings. Another strain called Legionella longbeachae occurs in soils, composts and potting mixes, and is responsible for more than half of all New Zealand cases.


It usually takes 2-10 days for symptoms to develop after you have been infected.  Fever, and chills, muscle aches and pains, headache, cough, (often dry), abdominal pain, diarrhoea and severe exhaustion are common symptoms. Chest infection can progress to pneumonia which may be severe.  A mild form called Pontiac fever may occur with the same initial symptoms but it does not cause pneumonia and patients recover within a few days.

Contact your GP or Healthline (0800 611 116) for further advice.

How is it spread?

The illness is spread by breathing dust or water particles containing the bacteria. People who have Legionella disease cannot infect others.  The disease is only caught from the Legionella bacteria in the environment.


  • Ensure that your hot water cylinder at home is set to 600C (a tempering valve should be used to lower the water temperature at taps to reduce the risk of scalding)
  • If you work in a building that has a water-cooled ventilation system it should be regularly maintained and tested according to industry standards
  • When working in the garden minimize the amount of dust by wetting soil first
  • Wear gloves when handling soil, mulches, compost or potting mix
  • Wear a dust mask when opening bags or using potting mix and compost to avoid inhaling dust.
  • When using potting mix or compost always open the bag slowly in a well ventilated area away from your face. Always dampen the potting mix or compost before using it
  • Make sure the working area (glasshouse, potting shed) is well ventilated
  • Water the garden and indoor plants using a gentle spray
  • Wash hands thoroughly after working with soil, potting mix or compost.

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