Legionnaires’ disease

Legionnaires’ disease, also known as legionellosis, is an infection of the lungs (pneumonia) by bacteria of the Legionella family. Infection occurs when a person breathes in bacteria that are commonly found in the environment.

Almost all patients diagnosed with Legionella infection will need to be admitted to hospital for treatment. Legionnaires’ disease can cause death if not treated in time.

Symptoms

The early symptoms of Legionnaires’ disease are typically similar to influenza-like illness and may include:

• fever
• chills
• muscle ache
• headache
• tiredness
• lethargy
• loss of appetite
• diarrhoea.

People can become very sick with pneumonia (infection of the lungs) and develop cough (usually ‘wet’ or productive), shortness of breath or have difficulty breathing.

How Legionnaires’ disease is spread

Legionnaires’ disease can occur after a person inhales or breathes in water vapour or dust that is contaminated with Legionella bacteria. Although there are many different species of Legionella, the two that most commonly cause disease are Legionella pneumophila and Legionella longbeachae.

Legionella pneumophila naturally occurs in warm water environments. It poses a risk when the warm water is aerosolised (i.e. turned into water vapour, mist or steam) and is inhaled.

L. pneumophila can be found in the water of untreated or contaminated:

• Air conditioning cooling towers (in large buildings) and evaporative air conditioners
• Hot water systems and plumbing (particularly if not used for some time)
• Spa pools and baths
• Fountains
• Rain water tanks and sprinkler systems
• Inappropriately maintained home humidifiers and CPAP machines (used to treat obstructive sleep apnoea)
• Commercial car washes.

Legionella longbeachae naturally occurs in soil and gardening products, and poses a risk when dust from these products is inhaled.

L. longbeachae can be found in gardening products such as:

• potting mixes
• gardening soils
• mulches
• composts
• soil conditioners.

People may be exposed to Legionella bacteria at home, at work, or in a public places. The time between a person’s exposure to the bacteria and becoming sick is between 2-10 days, usually 5-6 days).

Legionnaires’ disease is not spread from person-to-person.

Who is at risk of infection

Some people are more likely to contract Legionnaires’ disease, including:

• people over 50 years of age
• smokers
• people with chronic health conditions such as:
  • lung disease
  • diabetes
  • kidney disease
• people with weakened immune systems, including:
  • those on immunosuppressive medication
  • those who are otherwise immunosuppressed due to another health condition (such as HIV or certain cancers)
• men are also more commonly affected than women.

Diagnosis

It is often 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 laboratory tests.

Tests of sputum (mucus coughed up from respiratory tract), blood, and/or urine samples can sometimes quickly confirm the diagnosis. Sometimes two blood samples taken three to six weeks apart are required to serologically confirm the diagnosis.

Treatment

Legionnaires’ disease can usually be cured by treatment with appropriate antibiotics. For serious infections, patients may need to be cared for in an intensive care unit and have their breathing assisted on a ventilator.

Prevention

L. pneumophila bacteria can 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. All water-based air conditioners, hot water systems, spas and other equipment (eg humidifiers and CPAP machines) should be maintained and cleaned as per the manufacturer’s instructions to prevent growth of L. pneumophila.

L. longbeachae is common in the soil and other gardening products. Infection can be prevented by reducing your exposure to dust.

This can be done by following the manufacturers' warnings (present on labels/packaging of garden supplies), including:

• wetting down the potting mix/mulch/soil etc. before distributing to reduce dust.
• wearing gloves and a P2 mask (available from hardware stores) when handling or distributing potting mix/mulch/soil.
• washing your hands after handling potting mix/mulch/soil, and before eating, drinking or smoking.

More information

Legionella infection is a notifiable condition. For more information about Legionella, contact your GP or call the Health Protection Service, Communicable Disease Control Information Line during business hours on 02 5124 9213.

Acknowledgements

• Heymann DL, 2015, Control of Communicable Diseases Manual, 20th edition.
• NSW Government, NSW Health, Legionnaires disease fact sheet
• Government of WA, Department of Health, Legionnaires’ disease fact sheet