Victoria's acting Chief Health Officer has warned gardeners about the potentially deadly risks associated with everyday potting mixes as spring is typically a time when Victorians are more likely to be gardening.

Dr Sutton said notifications of illness caused by infection with Legionella longbeachae, a bacteria commonly found in potting mix continue to be made.

"To many gardeners, potting mix may seem harmless, but it can actually be very dangerous unless the correct procedures are followed," Dr Sutton said.

"Most people who breathe in the bacteria do not become ill. The risk of disease is increased with age, smoking, and in people with weakened immune systems."

Legionella longbeachae is one cause of Legionnaires' disease. It is found in tiny quantities in the general environment (including soil) and is not normally a health hazard. But the ingredients and dampness of potting mix make it the ideal breeding ground for the bacteria.

Legionella longbeachae is different to Legionella pneumophila, the more well-known cause of Legionnaires' disease found in poorly maintained cooling towers and spas.

Dr Sutton said gardeners using potting mix should always follow the manufacturer's safety instructions on the bag.

To minimise the risk of contracting Legionnaires' disease from soil, compost or potting mix, gardeners should take 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;
  • 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; and
  • Avoid breathing in droplets of water from dripping pot plants, including hanging baskets, and when watering plants.

Dr Sutton said so far this year there had been 7 cases of Legionella longbeachae, with 24 cases last year and 12 in 2016. A higher number of cases are reported during spring, with a peak in November.

Legionnaires' disease can be fatal in a small number of people who have severe illness. Infection with Legionella longbeachae bacteria is responsible for around 18 per cent of all legionella cases in Victoria.

He said different types of legionella bacteria all cause a rare form of atypical pneumonia. Early symptoms include fever, chills, headache, shortness of breath, sometimes dry cough, muscle aches and pain. People who suspect they may be ill should visit their doctor.

Further information about Legionella can be obtained from the Better Health Channel or by contacting the Legionella Program on 1300 767 469.

Contact details