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Occupational disease focus: Legionnaires’ and Pontiac Fever
The Australian Department of Health reports the highest number of notifications for Legionella infections is during autumn. It is important for workplaces to understand the risks posed and how these can be reduced.
Legionella
Legionella bacteria, first identified in the mid-1970s, causes a range of disease which remains prevalent and is without vaccine.
The mortality rate from Legionella infection is usually ranges between 5 to 10 per cent, yet worldwide it may be as high as 40 to 80 per cent in untreated immune-suppressed patients. Fortunately, early antibiotic treatment greatly improves the rate of survival.
Legionella infections can cause serious respiratory illness ranging from a short flu-like condition (Pontiac Fever) to severe pneumonia (Legionnaires’ disease) or organ failure.
Legionella bacteria naturally inhabit fresh water ponds, streams, lakes, rivers, underground and brackish water and is found in soil and mud.
The Legionella bacteria thrives in domestic and commercial plant and machinery where there are warm, moist conditions.
Legionella infections are most commonly linked to cooling towers, air conditioning units and garden soils.
Around 400 cases of Legionella infections are reported to the Australian Department of Health annually.
Western Australia comprises about 95 of those cases, with an approximate 80/20 split of Pontiac fever and Legionnaires’ disease respectively.
In Western Australia, the Occupational Safety and Health Act 1984 (the OSH Act), the Mines Safety and Inspection Act 1994 (the MSI Act), require the notification of Legionnaires’ disease.
Legionnaires' disease
Legionnaires’ disease is a severe form of pneumonia. Infection is caused from inhaling droplets or mists of water infected with Legionella bacteria.
The risk of contracting Legionnaires’ disease can be reduced to very low through the careful design, installation and regular maintenance of cooling towers, air-handling systems, hot water services and other potential sources of water vapour.
Legionella is known to accumulate in:
evaporative condensers; hot and cold water systems; spas; humidifiers, foggers and water misting systems; industrial milling machines coolant; high pressure cooling and cleansing processes, such as drill-sprays and high pressure washers; potable water aerosols, such as shower heads; nebulisers other domestic and industrial-based water systems.
Legionella survives in water between 20-50 o C and thrives in 25-42 o C and is promoted by:
stagnant or low turnover water; high concentrations of algae, amoeba, slime and other bacteria; presence of biofilm, scale, sediment, sludge corrosion products or other organic matter; degraded plumbing materials, such as rubber fittings, which may provide nutrients to enhance bacterial growth.
Legionnaires' symptoms
The incubation period for Legionnaires’ disease is usually two to ten days.
Acute infections can affect bodily systems leading to diarrhoea, vomiting, mental confusion and kidney failure.
Early symptoms of Legionnaires’ disease can include some or all of the following:
fever up to 40oC; chills aching muscles and joints dry cough; headaches tiredness gastro-intestinal disorders loss of appetite shortness of breath.
Pontiac Fever
In Australia, a common type of Legionella illness is Pontiac fever.
Legionella longbeachae bacteria causes Pontiac fever and is found in potting mix, garden soils, mulch or compost. Infection occurs with inhalation of dust or aerosolised particles from contaminated soil.
Legionella longbeachae also forms in water systems especially if these are infrequently used or not regularly maintained. Examples include: evaporative air conditioners; artesian bores; decorative fountains; fire sprinklers; fixed garden sprinklers; commercial aquariums; car washes; water-based dust suppression systems; above ground storage tanks, which feed aerosol generating equipment; any water system generating an aerosol where the water temperature ranges between 20oC and 45oC.
Risk factors
Legionella pneumophila can be transmitted through inhalation of aerosolised water droplets. Drinking and washing in water containing low numbers of Legionella bacteria is not known to cause infection.
Factors increasing the likelihood of infection: smoking; chronic heart or lung disease; diabetes; HIV/AIDS; some forms of cancer; steroid or immunosuppressive medication; renal disease or kidney failure; being over 50 years of age and/or being male excessive alcohol consumption.
Reducing the risks
Pontiac fever
Safe handling of potting mix, garden soils and compost will reduce the risk of inhaling contaminated aerosols. To minimise the risk of infection, workers are advised to: open bags with care to avoid inhaling airborne particles; moisten the contents to avoid creating dust; wear gloves and an appropriate mask; wash hands after handling potting mix, even if gloves were used.
Legionnaires disease
Identify all sources of water that generate aerosols or mists, especially where conditions are known to enable Legionella to accumulate and thrive, and:
assess the risk of exposure to the sources; review risk management strategies for tasks that generate aerosols; implement controls to restrict Legionella growth and prevent exposure; apply the hierarchy of controls: – use alternate, clean water sources; – use engineering controls, such as residual biocides, drift-eliminators, or extraction ventilation; – if required, use personal protective equipment, such as respirators; implement a Legionella monitoring strategy to verify control effectiveness; enact planned maintenance, remedial treatment or corrective actions to prevent Legionella; ensure work site emergency response plans includes management of infection outbreaks.
Did you know?
Legionnaires’ disease is a prescribed disease under the OSH and MSI Acts and must be reported to the Department.
Legionella infection is also specified under the Public Health Act 2016 and is a notifiable disease in Western Australia.
Legionella pneumophila infection must be reported urgently by telephone to a public health unit.
Guidance material
Prevention and control of Legionnaires’ disease – code of practice
Reporting and notification
Report an injury or disease, Department of Mines, Industry Regulation and Safety
Notification of infectious disease and related conditions, Department of Health
