Legionnaires' disease

Legionnaires’ Disease is a serious and potentially fatal form of pneumonia caused by the bacteria Legionella pneumophilia. People usually get Legionnaires’ Disease by breathing in Legionella bacteria in very fine droplets of water called aerosols.  

As Legionella bacteria thrive in warm water and warm damp places, man-made water systems can provide environments that let Legionella bacteria increase to large numbers. These man-made systems include:

  • cooling towers and evaporative condensers
  • evaporative air conditioners
  • warm water systems (e.g. showers)
  • misting or droplet spray systems
  • car washes
  • spa pools and hydrotherapy pools
  • fountains
  • ice machines

Refer to the Healthy WA website for further information about the signs, symptoms and treatment of Legionnaires’ Disease.

Legionella statutory notification

Legionella is a notifiable infectious disease in WA.

Any medical practitioner or nurse practitioner attending a patient whom he/she knows, or suspects has a notifiable infectious disease or a related condition, which includes Legionella pneumophila, has a legal obligation to report the diagnosis to the WA Department of Health under the Public Health Act 2016.

This information is used to trace the potential source of infection, investigate outbreaks and inform public health actions to be taken.

For more information:

Pontiac Fever

Pontiac Fever is a milder infection that can also be caused by poorly maintained cooling towers and water systems.

Symptoms begin between a few hours to 3 days after being exposed to the bacteria and usually last less than a week.

Pontiac Fever is different from Legionnaires’ Disease because someone with Pontiac Fever will not get pneumonia. Pontiac Fever is also caused by Legionella bacteria. By addressing the risks of Legionnaires’ Disease, the risks of Pontiac Fever is also managed.