Legionnaires' disease (legionellosis)

Legionnaires' disease is a chest infection (pneumonia) caused by the Legionella bacteria. People usually catch the disease by breathing in water droplets that contain the bacteria from sources like soil, compost, potting mix, or spa pools and water systems.

Symptoms of Legionnaires' disease

Symptoms include a 'flu-like' illness with:

  • cough
  • shortness of breath
  • high fever
  • muscle aches
  • runny poos (diarrhoea)
  • feeling sick or throwing up
  • stomach pain
  • headaches
  • excessive sweating.

You may have mental confusion and disorientation may develop. The illness worsens over several days.

Causes of Legionnaires' disease

Legionnaires' disease is not common in Aotearoa New Zealand. Most people’s natural immunity stops them from getting ill when exposed to the bacteria.

Anyone can get Legionnaires' disease. You may be more likely to catch it, and the effects may be more serious for you if you:

  • are over 50
  • smoke or used to smoke
  • have a long-term illness — especially lung disease
  • a weakened immune system.

People catch legionnaires' disease by breathing in water droplets that contain 'Legionella' bacteria, or after inhaling dust from soil. The most common source of the bacteria is potting mix or compost. Other sources are piped hot water, air conditioners and spa pools.

Once in the lungs, the bacteria multiply and may cause disease. The infection is not contagious and cannot be caught from another person.

Diagnosing Legionnaires' disease

If you have any of these symptoms and have recently been handling potting mix or compost, see your usual doctor or healthcare provider as soon as possible. Make sure you tell them that you have been in contact with these products.

Legionnaires' disease is diagnosed from a mucus or phlegm (sputum) sample. You may also have a blood test and a chest x-ray.

Treating Legionnaires' disease

It is important to get early treatment early. Legionnaires' disease is treated with antibiotics.

Preventing Legionnaires' disease

To avoid getting Legionnaires' disease, be very careful when using potting mix, seed raising mix, compost or other soil products. It is very important that you do not inhale the dust from any of these products.

To keep yourself safe:

  • wear a disposable face mask and gloves when opening bags of potting mix or other soil products
  • open bags carefully away from your face, using scissors rather than ripping the bag
  • do your potting outside, in a well ventilated area
  • use a sprinkle of water to dampen down potting mix or compost to stop the dust from spreading in the air
  • wash your hands thoroughly after touching potting mix or soil products or after doing any gardening.

Clinical review

This content was written by HealthInfo clinical advisers. It has been adapted for Health Information and Services.

Clinical advisers — HealthInfo (external link)

Last updated: