Legionellosis or Legionnaires’ disease is caused by Legionella bacteria that live in the environment, especially in soil, composts, potting mixes and water.

People can get Legionella after inhaling mist or spray from water containing Legionella bacteria, or from inhaling dust from soil containing the bacteria.

It cannot be spread from person to person.

To reduce the risk of getting legionellosis:

  • ensure your hot water cylinder is maintained at 60 degrees 
  • take care when dealing with potting mix, soil or compost.

If you are concerned about legionellosis or Legionnaires’ disease, call Healthline on 0800 611 116 or see your doctor or practice nurse.

There are many types of Legionella bacteria. They can be found in any type of water, and in soil. They have been found in roof water tanks, drinking water pipes, spa pools and all different types of soil, potting mixes and composts. Legionella are particularly common in warm stagnant water.

People can get Legionnaires’ disease after breathing in mists or spray (aerosols) from a water source that contains Legionella bacteria, or after inhaling dust from soil or compost. You cannot get it by drinking contaminated water, and it cannot be passed from one person to another.

Legionnaires’ disease symptoms include fever, chills, dry cough, muscle aches and pains, headache, diarrhoea and extreme tiredness.

It usually takes two to 10 days after exposure to the bacteria for symptoms to develop.

If you have symptoms

If you think you have Legionnaires’ disease, see your doctor. You will usually need to have a sputum (mucus/phlegm) test to confirm if you have the disease, and you may need a chest X-ray.

Legionnaires’ disease needs treatment with antibiotics, and most cases can be treated successfully. Healthy people usually get better after being sick with the disease, but they often need hospital care.

You can return to work when you feel better. There is no risk of infecting others.


To reduce your risk of Legionnaires’ disease from water

To reduce the risk of Legionnaires’ disease from water, maintain the temperature of your household hot water cylinder at a minimum of 60°C. To ensure that water is delivered from the tap at a safe temperature, mixing valves – usually put underneath your sink – are highly recommended, and are required in new buildings. Mixing valves are the best way to ensure a safe water temperature at the tap, and can be fitted to older houses.


To reduce your risk of Legionnaires’ disease from soil

Do the following to reduce the risk of Legionnaires’ disease from soil, compost and seed and potting mixes.

  1. Wash your hands thoroughly after handling compost or gardening, even if you were wearing gloves.
  2. Minimise dust when working in the garden. Dampen dry compost heaps before turning or use. Water compost heaps and bedded plants using a gentle spray.
  3. Do your potting in a well-ventilated area, or outdoors.
  4. Instead of ripping them apart, open compost bags carefully using scissors. Open the bag slowly, and keep your head and face well clear.
  5. Avoid touching your face or mouth with your hands while gardening.
  6. Wear gloves when handling compost/soil.
  7. Fold over and clip (eg, with a clothes peg) the top of compost bags when not in use.
  8. Avoid storing compost in greenhouses, which heat up and encourage Legionella bacteria to grow.
  9. Store bagged compost in a cool, dry place.
  10. Consider wearing a P2-rated dust mask when handling potting mixes or turning compost. These should be thrown away after a day in the garden. A blue surgical COVID mask will also help reduce your risk.

Legionnaires’ disease is a notifiable disease. This means that health professionals or laboratories will inform us when someone has it. This allows us to look for sources, monitor the number of people who have the disease and give advice on how it can be prevented. 


There are specific requirements for notifiable diseases in the Auckland region.

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Last updated 22.11.2022

For health advice call Healthline for free anytime on 0800 611 116
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