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Issue Number #31
Issue Date Autumn 2005
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Title Legionnaires Disease

There have been reports of risks to health from Legionnaires disease, from handling potting soil. Here is some information from www.health.vic.gov.au

What is Legionnaire's Disease?

Legionnaires' disease (Legionellosis) is a serious and sometimes fatal form of pneumonia caused by the bacteria Legionella. Although not all cases of Legionnaires' disease are severe, up to ten per cent of cases can be fatal.

There are over forty strains of Legionella bacteria but only a few cause disease in humans. The strains that are most commonly associated with human disease are pneumophila and longbeachae.

What are the symptoms?

Legionnaires disease usually causes fever, chills and a cough that may be dry or may produce sputum. Some people also have muscle aches, headache, tiredness, loss of appetite and diarrhoea. People can become very sick with pneumonia; most people recover but the disease is occasionally fatal. It is not spread from person to person. The time between the patient's exposure to the bacteria and becoming sick is between two to 10 days.

Legionnaires disease most often affects middle-aged and older people, particularly those who smoke cigarettes or who have chronic lung disease. Also at increased risk are people whose immune systems are suppressed by medications or diseases such as cancer, kidney failure, diabetes or AIDS.

How is Legionnaires disease diagnosed and treated?

It is difficult to distinguish Legionnaires disease from other types of pneumonia by symptoms alone. Chest X-rays often show pneumonia but the diagnosis requires special tests. Tests of blood samples (taken three to six weeks apart), sputum and urine can be helpful for confirming the diagnosis.

Patients with Legionnaires disease may be treated in hospital with antibiotics through a drip. Some may need to be in an intensive care unit and may need assistance to breathe by a ventilator.

Where are Legionella bacteria found?

Legionella pneumophila is usually found in water sources, whereas another bacteria of the Legionella family, Legionella longbeachae is commonly found in soil and potting mix. Most reported cases of Legionnaires disease are caused by the water-borne strain, pneumophila, however several cases reported recently in Victoria had arisen from potting soil containing the longbeachae strain.

What precautions can be taken?

Because Legionella bacteria are commonly found in soils and potting mix, gardeners should:

  • Always wear a face mask and gloves when using compost and potting mix, including when opening the bag.
  • Moisten the contents of potting mix bags to avoid creating dust.
  • Always wash hands after handling potting mix.
  • Potting soil should be stored in a cool location and cleaned up while the product is damp.


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