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Potting mix warning following death of Dunedin gardener

November 2019

The recent death of a Dunedin man has prompted Public Health South to remind spring gardeners of the need to handle potting mix and compost with care.

The man is thought to have been infected while adding compost to a glasshouse. He initially developed flu-like symptoms, visited his GP and was admitted to hospital. The man’s condition gradually deteriorated and he died within a week of onset of the disease. .

Legionnaires' disease, also known as legionellosis, is a type of pneumonia caused by the legionella bacteria, commonly found living in potting mix, soils and compost.

Medical Officer of Health Dr Anura Jayasinghe says that people should watch out for signs of legionellosis as early treatment is usually effective.

“Early symptoms can appear 2-10 days after exposure and are similar to the flu. The infection can cause a cough, shortness of breath, high fever, muscle pains, and headaches. Nausea, vomiting, and diarrhoea may also occur.”

Older people, people who smoke and those with lowered immunity have less resistance to the legionella bugs.

Anyone handling potting mix, soils or compost should:

• Wear a good quality, double strap mask that fits well and covers the nose and mouth
• Wear gloves to protect against skin infections and prevent spreading the legionella bug (such as to your mouth)
• Open bags in a well ventilated space, away from the face.
• Wash hands when finished

Further information on working safely with potting mix, soils and composts as well as how to prevent Legionnaires’ disease from air conditioning systems can be found at the WorkSafe website

What is Legionnaires’ disease or legionellosis?
Legionellosis is a respiratory infection caused by inhaling the legionella bacteria. Most cases occur as single isolated events, but outbreaks do occur.

What are the symptoms?
Many legionella infections are never diagnosed because the symptoms are either absent or very mild. When symptoms do occur, there are two distinct forms of the disease: Legionnaires’ disease and Pontiac fever. Both forms of illness begin with flu-like symptoms, including fever, loss of appetite, tiredness, body aches, cough, shortness of breath, headache and occasionally diarrhoea. Chills and a rapidly rising fever are usually seen within 24 hours. Persons suffering from Pontiac fever recover within 2-5 days without treatment. Those with Legionnaires’ disease may develop pneumonia.
The symptoms for Legionnaires’ disease can appear between 2-10 days (usually 5-6 days) after exposure to the bacteria. For Pontiac fever, symptoms occur between 5-66 hours, most often between 24-48 hours.

Where are legionella bacteria found?
Legionella bacteria are widespread in our environment and usually do not cause illness. They live in soil, compost and potting mix and aquatic environments such as rivers, lakes and reservoirs. They prefer warm, moist conditions and have been found in hot water systems, water in cooling towers, evaporative condensers of large air conditioning systems, spas and hot and cold taps.

How is it spread?
People can get legionellosis after inhaling dust from soil, compost or potting mix or mists or sprays (aerosols) from a water source that contains legionella bacteria. Legionella bacteria cannot be passed from one person to another nor can it be acquired by drinking contaminated water.

Who gets legionellosis?
Men and women of any age can get legionellosis, but middle-aged or older men, particularly those who smoke or drink heavily, are at higher risk. People with chronic illnesses such as lung disease or those with problems with their immune system are also at greater risk. The disease is very rare amongst children.

How is it treated?
Your doctor will prescribe specific antibiotics to treat legionellosis.

How is it prevented?
The risk of acquiring a legionella infection is greatly reduced by taking care when dealing with compost, potting mix and any form of soil or dirt. To reduce the risk of inhaling dust from these mixes you should:
• read the warning labels on commercial bags of potting mix and compost and follow the advice provided
• wear a well fitted face mask (N95 or P2) and open the bag away from your face in a well ventilated space
• open bags carefully using scissors rather than ripping the bag open
• dampen down the potting mix or compost with a sprinkle of water to prevent it blowing around your face. The Ministry of Health have a pamphlet ‘Safer and Healthier Gardening’ which also contains advice on protection from legionella bacteria while gardening


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