Legionnaires’ disease is a form of lung infection (pneumonia) caused by Legionella bacteria.
Legionella is commonly found in natural water sources such as rivers, lakes, and hot springs, as well as in spas, potting mix, warm water systems and artificial systems that use water for cooling, heating or industrial processes (i.e. cooling towers).
A person may catch Legionnaires’ disease by breathing in fine water droplets containing the bacteria. Legionnaires’ disease cannot be spread from person-to-person or from drinking contaminated water.
Symptoms usually appear 2-10 days after exposure to Legionella bacteria and include cough, shortness of breath, fever, headache, chills, and muscle aches.
Legionnaires’ disease can lead to serious illness and may require hospitalisation. If you develop symptoms of Legionnaires’ disease, you should seek urgent medical care through your GP or local healthcare provider.
Who is most at risk?
Not everyone who breathes in Legionella bacteria will become unwell. Whilst disease is rare in children and healthy adults, those at greater risk of developing Legionnaires’ disease include:
- People over the age of 65
- Smokers or heavy drinkers
- People with chronic lung disease
- People with underlying medical conditions such as diabetes, cancer or kidney failure
- People with a weakened immune system (immunocompromised)
How can you protect yourself from Legionnaires’ Disease?
There is no vaccine to prevent Legionnaires’ Disease, but there are things you can do to protect yourself from contracting the infection.
Make sure that artificial water systems like hot water systems, spa pools, and evaporative air conditioners are properly maintained, cleaned, and disinfected to prevent the growth of bacteria.
Additionally, when handling potting mix or gardening, wear a mask and gloves, and take care to avoid inhaling dust or droplets, especially when opening bags or watering plants.
Public Health management of Legionnaire’s disease
Legionella is urgently notifiable to the Victorian Department of Health, allowing for prompt public health investigation and management of all diagnosed cases. Surveillance is a key part of the public health response, helping to identify any increase in case numbers above the normal level.
NEPHU thoroughly investigates any cluster or outbreak of legionellosis cases with the assistance of specialised teams from the Department of Health. This often includes an in-depth interview with people diagnosed with the infection, as well as testing and disinfecting potential sources of Legionella such as cooling towers of air-conditioning units.
During these investigations official health alerts or media coverage may be used to raise awareness in the community, and to encourage assessment and testing for legionella. Whilst it is good to be aware of at-risk areas, there is no need to alter your usual behaviours or stop routine daily activities in these locations.
As legionella is common in the environment, investigation does not always identify a specific source, however return of legionella notifications to baseline numbers often indicates an outbreak source has been adequately managed or has self resolved.
For clinicians
If you suspect Legionella:
- collect urine for Legionella urinary antigen testing. If pneumonia is present, consider requesting Legionella culture and PCR on lower respiratory tract sample if available (e.g. sputum, bronchoscopy samples)
A positive culture enables genomic analysis and matching isolates with environmental samples.
- A positive culture enables genomic analysis and matching isolates with environmental samples
- Legionella serology requires two serial samples, initial and convalescent (3 to 6 weeks later) to identify new or previous legionella infection
For treatment advice refer to the Therapeutic Guidelines or consult with your local infectious diseases service.
Legionellosis is an urgent notifiable condition that must be notified to the Local Public Health Units upon initial diagnosis or clinical suspicion by calling 1300 651 160.
