Legionnaires’ Disease: What It Is, How to Prevent It & How to Know If You Have It

Some of you may have seen or read about the recent legionella outbreak in Melbourne which is though responsible for the hospitalisation of 5 people who contracted Legionnaires’ disease.  Health authorities in Victoria suspect that the source of the Legionella may have been cooling towers in the Melbourne CBD.  Consequently, the authorities ordered the disinfection of 89 cooling towers in the CBD.

So, What Is Legionnaires’ Disease?

Legionnaires’ disease is caused by respiratory infection with the Legionella bacteria which is present in the natural environment and which can proliferate in water that provides the correct conditions for the bacteria to multiply.  Some environments which can promote legionella growth if not correctly managed include water tanks, water management systems (including drinking water and warm water systems), cooling towers, fountains and ice machines.

Most office and retail premises within our cities have one or more cooling towers as part of the building’s air handling system.  It is vital that these cooling towers are appropriately maintained in order to ensure correct water chemistry and system integrity which does not promote bacterial growth and potential legionella proliferation.


Symptoms & Transmission of Legionellosis

Symptoms of legionellosis are typically flu-like in nature, with those affected exhibiting fevers, headaches, muscle aches and mild coughs. This illness progresses rapidly, developing into more serious symptoms like diarrhoea, vomiting, abdominal pain and chest infections. It usually takes 2 – 10 days for symptoms to appear, and because legionnaires’ disease is similar symptomatically to strands of pneumonia, diagnosis will always involve a blood or urine test. These tests may need to be repeated for confirmation.

Progress of the infection is rapid, so it is crucial to ensure that once diagnosed, you seek immediate care from a healthcare professional. With early and effective antibiotic treatment, symptoms usually subside within 3 to 5 days. Without treatment, legionellosis can lead to severe illness, kidney failure and in severe cases, death.

Legionnaires’ disease cannot be transmitted from person to person or animal to person, instead outbreaks occur from a group of people inhaling or encountering the bacteria in the same environment.

Legionellosis is uncommon in people under 50 and extremely rare in children. Those susceptible to the disease are people over 50, cigarette smokers and those with a weak immune system because of a chronic illness.

legionnaires disease

Minimising the Risk of Legionella

Both Queensland Health and WorkSafe Queensland provide guidance on the management of water handling systems, including cooling towers in order to minimise the risk of Legionella growth.  Guidelines for maintenance of cooling towers and sampling for Legionella are provided in Australian Standard series AS3666 Air handling and water systems of buildings- Microbial Control.  AS3666.3 states: The primary aim is to avoid conditions that may allow microorganisms, including legionellae to multiply in the cooling water system thus creating a health risk. The standard recommends that a risk assessment of the cooling tower system is carried out by a competent person.

There are many factors within a cooling tower system that can lead to increased risk of legionnaires.  Some include:

  • Presence of water (especially if stagnant, e.g. dead legs or system not in use)
  • Concentration of legionellae (all species are considered as potential pathogens)
  • Concentration of other heterotrophic bacteria
  • Presence of protozoa and algae
  • Presence of nutrients
  • System size [surface area available for biofilm development (compared with water volume)]
  • Presence of biofilm
  • Water quality
  • Water temperature
  • Characteristics of make-up water (physical, chemical, microbiological)
  • Direct sunlight (which promotes algal growth)
  • Physical condition of system
  • Microbial control program
  • System location and environment
  • Aerosol generation
cooling tower

How Tony Lane Consulting Can Help You

So, as you can see, there are many factors at play and it is clear that the advice of an independent and competent person should be sought in order to assure owners, managers and tenants (not to mention members of the public) that everything practicable is being done to minimise the chance of a legionella outbreak.

Tony Lane Consulting have the experience and expertise to conduct a comprehensive risk assessment of your cooling tower systems.  We utilise the methodology of Australia’s most rigorous guidelines, A Guide to Developing Risk Management Plans for Cooling Tower Systems.  This is published by the Victorian Department of Human Services and utilised as part of a mandatory approach to Cooling Tower Risk Assessment under Victorian WHS Legislation.

Call Tony Lane Consulting today for an obligation free quote.

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