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Health Warning Issued for Potting Mix

Health warning potting mix

The Department of Health has been notified of 34 cases of Legionella longbeachae infection from 1 January to 6 October 2021.  There were 44 cases reported in 2020, and 38 cases in 2019. 

While Legionella longbeachae is found in tiny quantities in the general environment (including soil), it is not normally a health hazard. However, the ingredients and dampness of potting mix make it the ideal breeding ground for the bacteria.

Legionnaires’ disease can be fatal in a small number of people who have a severe illness.

The number of cases usually peak around autumn and spring as infections are common during the time when people are most likely to garden so it is very important gardeners are aware of this risk and take steps to reduce the risk of exposure.

Legionella longbeachae is different to Legionella pneumophila, the more common cause of Legionnaires’ disease found in poorly maintained cooling towers and spas.

Who is at risk?

Most people who breathe in the bacteria do not become ill. However, the risk of disease is increased with age, smoking, and in people with weakened immune systems. People most at risk include those who:

  • are older (over 65 years of age) 
  • smoke
  • drink heavily
  • have chronic lung disease
  • have underlying medical conditions such as diabetes, cancer or kidney failure; or
  • have a weakened immune system (e.g. from taking steroidal medications, undergoing chemo- or radiotherapy). 

Symptoms and transmission

The symptoms of Legionnaires’ disease usually begin to appear within six days of being exposed to the bacteria. Early symptoms are like the flu and include fever, chills, headache, shortness of breath, sometimes dry cough, muscle aches and pain. 

Sometimes other systems in the body are affected. This can cause diarrhoea, mental confusion and kidney failure.


If clinicians suspect Legionella longbeachae infection, the following tests can help confirm the diagnosis:

  • Legionella polymerase chain reaction (PCR) and/or culture from a sputum sample; or
  • Paired serology.

Legionnaire’s disease is an ‘urgent’ notifiable condition that must be notified to the department by medical practitioners and pathology services. Notify the Department of Health on 1300 651160 (24/7). Gardeners can reduce the risk of contracting Legionnaires’ disease from soil, compost or potting mix, by taking the following precautions:

  • Always wear a mask and gloves when handling soil, compost or potting mix
  • Wash hands carefully with soap and water after handling soil and before eating, drinking, smoking or placing hands near the face or mouth
  • Follow the manufacturer’s safety instructions on the potting mix bag.
  • Store bags of potting mix in a cool dry place. When stored in the sunlight, the temperature inside the bag can increase, creating an ideal environment for Legionella bacteria to grow
  • Open bags in a well-ventilated space
  • Open bags of composted potting mix slowly, directing the opening away from the face to avoid inhaling the mix. Wet the soil to reduce dust when potting plants
  • Water gardens and composts gently, using a low-pressure hose
  • Avoid breathing in droplets of water from dripping pot plants, including hanging baskets, and when watering plants
  • Anyone with concerns about their health, should seek medical attention.