Legionnaires disease is an infection of the lungs (pneumonia) caused by Legionella bacteria . It is difficult to distinguish Legionnaires disease from other types of pneumonia by symptoms alone.
Last updated: 01 July 2012

What is Legionnaires disease?

  • Legionnaires disease is an infection of the lungs (pneumonia) caused by bacteria of the Legionella family.
  • Infection occurs when a person breaths in bacteria that are commonly found in the environment.

What are the symptoms?

Legionnaires disease usually causes fever, chills, a cough and shortness of breath. 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.

How is it spread?

  • Legionnaires disease can occur after a person breathes in contaminated water vapour or dust.
  • Although there are many different species of Legionella bacteria, the two that most commonly cause disease in NSW are Legionella pneumophila and Legionella longbeachae
  • Legionella pneumophila bacteria can contaminate air conditioning cooling towers, whirlpool spas, shower heads and other bodies of water.
  • Legionella longbeachae can contaminate soil or potting mix.
  • People may be exposed to the bacteria at home, at work, or in public places.
  • Legionaires disease 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.

Who is at risk?

Legionnaires disease most often affects middle-aged and older people, particularly those who smoke 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 it prevented?

  • Legionella pneumophophila grow to high numbers in warm, stagnant water. Outbreaks are sometimes associated with contaminated cooling towers (that are part of air conditioning systems in large buildings). Regular inspections, disinfection and maintenance of cooling towers and plumbing systems limits the growth of the bacteria.
  • Legionella longbeachae is common in the soil and potting mix. Reduce exposure to potting mix dust by following the manufacturers' warning present on potting mix labels, including:
    • Wet down the potting mix to reduce the dust.
    • Wear gloves and a P2 mask when using potting mix.
    • Wash your hands after handling potting mix or soil, and before eating, drinking or smoking.

How is it diagnosed?

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

How is it treated?

Legionnaires disease can usually be cured by treatment with antibiotics.
Some patients may need to be in an intensive care unit and may need assistance to breathe using a ventilator.

What is the Public Health response?

Laboratories and hospitals are required to confidentially notify cases of Legionnaires disease to Public Health Units in NSW. Public health unit staff interview patients or their carers about their illness and possible exposures. Where two case are linked, then possible sources of infection (such as cooling towers) are assessed and if necesssary cleaned.

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For further information please call your local Public Health Unit on 1300 066 055