What is Legionnaires’ disease?
What are the symptoms of Legionnaires’ disease?
How is it caused?
Who is at risk?
How has NSW been affected by Legionnaires’ disease?
What is the NSW Health system doing about the Legionnaires’ outbreaks?
What precautions do people need to take to reduce their chance of contracting Legionnaires’ disease?
How are cooling towers contaminated?
How are cooling towers regulated?
What causes an outbreak of Legionnaires’ disease?
What is the public health response to Legionnaires’ cases?
What happens when two patients report common exposures?
What happens when three patients report common exposures?
When are deaths publically reported?
How can you determine the source of an outbreak?

What is Legionnaires’ disease?

Legionnaires’ disease is an uncommon infection of the lungs (pneumonia) caused by Legionella bacteria. The bacteria are commonly found in the environment, particularly water and soil. Infection occurs two to 10 days after a person breathes in the bacteria in contaminated water vapours or dust.

What are the symptoms of Legionnaires’ disease?

Symptoms of Legionnaires’ disease include fever, chills, a cough and shortness of breath. Some people also have muscle aches, headache, tiredness, loss of appetite and diarrhoea. People can become very sick with pneumonia; most people recover, but around 10 per cent of patients die.

How is it caused?

There are many different species of Legionella bacteria but the two that most commonly cause disease in NSW are Legionella pneumophila (found in water) and Legionella longbeachae (found in soil). Legionella pneumophila bacteria can contaminate air conditioning cooling towers, whirlpool spas, shower heads and other bodies of water. Legionella longbeachae can contaminate soil or potting mix. People may be exposed to the bacteria at home, at work or in public places. Legionnaires’ disease is not normally spread from person to person.

Who is at risk?

Legionnaires’ disease most often affects middle-aged and older people, particularly those who smoke or who have chronic lung disease.  People whose immune systems are suppressed by medications or diseases such as cancer, kidney failure, diabetes or AIDS are also at increased risk.

How has NSW been affected by Legionnaires’ disease?

As at 22 December 2016, 121 cases of Legionnaires’ disease had been reported in NSW, with 34 due to Legionella longbeachae (generally associated with exposure to soils) and 87 due to Legionella pneumophila (associated with exposure to contaminated water vapour, such as that from cooling towers). See NSW Health’s latest statistics on Legionnaires’ disease​.

Previous years have seen about 100 cases of Legionnaires’ disease reported in NSW each year, with about two thirds of these caused by Legionella pneumophila.  Most cases are not found to be related to other cases, but some occur in clusters, or outbreaks.

The development of more sensitive tests and the more widespread use of these tests have contributed to better diagnoses and reporting of cases in NSW and elsewhere. Recent increased awareness of the disease among clinicians, in part thanks to NSW Health’s media alerts and direct communication to GPs and hospitals, is also likely to have increased the diagnoses of previously unrecognised cases.

There is no indication of a long term real increase in cases. The identification of recent outbreaks may be due to better detection of cases and the longer season of warm weather that may be associated with extended use of air-conditioning systems (involving cooling towers) into autumn, although the exact reasons remain unclear.

What is the NSW Health system doing about the Legionnaires’ outbreaks?

NSW Health’s public health units actively investigate all cases of Legionnaires’ disease. Their investigation includes:

  • interviewing cases and their families about possible exposures
  • checking the diagnosis with the doctors and laboratories
  • actively seeking additional cases that may have not been reported
  • working with councils where a  cluster is identified to inspect and, if necessary, test and have cleaned any suspicious sources, such as dirty cooling towers
  • in addition, letters have been sent to building owners in areas around where clusters have been identified urging them to comply with the public health regulations
  • media alerts have also been issued where clusters of three or more cases have been confirmed.

Public health investigation into the Legionella outbreaks in Sydney CBD, March and May 2016

This report summarises the findings of the public health investigations into Legionella outbreaks in Sydney CBD, March and May 2016. The report outlines public health actions, case identification, environmental investigations, testing, results and actions taken.

Legionella Expert Panel

NSW Health established a Legionella expert panel to advise the Chief Health Officer on whether any new measures are required to strengthen prevention and control activities. The expert panel was comprised of public health physicians, environmental health officers, an infectious disease physician, a legal expert, industry experts, mechanical engineer and a local government representative. It reviewed existing regulations, policies and procedures in place in NSW, how they compare with other jurisdictions, both nationally and internationally, and looked at lessons learned from the recent outbreak investigations. Members of the panel first met from April to late 2016.

While recognising that NSW already has had a strong regulatory system for preventing Legionnaire’s disease, the expert panel recommended strengthening it by further developing risk management plans for the operation of cooling towers.

A discussion paper was prepared to provide an overview of the current regulatory framework, the expert panel's recommendations, and to discuss how these are proposed to ​be implemented. The papaer was released in December 2016 and was open for public consultation until February 2017.

NSW Health received feedback on the discussion paper from 53 stakeholders, and a report on the discussion paper was released in July 2017: Report on public consultation: Proposed changes to the regulation of water-cooling systems to prevent Legionnaires’ disease iin NSW

Proposed regulatory changes

Proposed changes to the Public Health Regulations will require occupiers of premises with cooling towers to:

  • have risk management plans in place that are audited annually
  • undergo at a minimum monthly inspection, chemical analysis, and testing for Legionella and other bacteria
  • have unique identification numbers on each cooling tower
  • undertake specific remedial action in response to the detection of contamination.
The changes are expected to be made this year and occupiers will be given appropriate lead in time to implement the requirements. A Legionella Taskforce, including expertise in public health, water cooling systems and local government has been working to develop processes to support these measures. NSW Health is developing specific guidance on the roles and responsibilities of occupiers, risk assessors, auditors, authorised officers, industry and local government, procedures and protocols for responding to the new regulatory requirements, and facilitate processes for education and training. 


What precautions do people need to take to reduce their chance of contracting Legionnaires’ disease?

There are no specific precautions people should take in relation to the current clusters, however susceptible people who have been in areas where Legionnaires’ clusters have been detected should seek medical attention if they develop the following symptoms: fever, chills, cough, headache, aching muscles, lethargy. Legionnaires’ disease most often affects middle-aged and older people, particularly those who smoke or who have underlying health conditions such as chronic lung disease.

While exposure to contaminated water vapour from cooling towers and other sources may lead to a person to contracting the disease, Legionnaires’ disease can also be contracted through exposure to soil and potting mix where Legionella longbeachae may be found. NSW Health recommends reducing exposure to potting mix dust by following manufacturers’ warnings present on potting mix labels, including:

  • wet down the potting mix to reduce the dust
  • wear gloves and a P2 mask when using potting mix
  • wash your hands after handling potting mix or soil, and before eating, drinking or smoking.

How are cooling towers contaminated?

Cooling towers are devices that usually sit on top of large buildings as part of the air-conditioning system. They include a pool of water that is sprayed over pipes to cool the air inside the building. The water is then recirculated into the pool of the cooling towers. This pool of warm water provides ideal conditions for the growth of Legionella pneumophila. The water vapour from cooling towers tends to drift over the roof of the building down into the street beside the building, or may be blown some distance away, depending on the weather conditions. Should the water be contaminated, then people can be infected if they breathe it in.  

Due to the risk of contamination, cooling towers must be regularly and carefully inspected, disinfected and, where necessary, cleaned and decontaminated.  While regular testing is not necessary to keep the cooling towers clean, it can help in the maintenance process.

As a cooling tower is part of a building air-conditioning system, it is the responsibility of the building owner to ensure that it is maintained in a way to prevent contamination.

How are cooling towers regulated?

Public health laws in many jurisdictions regulate cooling towers to minimise the risk of contamination. In NSW:

  • building owners must register their towers with local councils
  • cooling towers must be regularly inspected, maintained and disinfected
  • cleaning must occur at least every six months and other specific checks occur at least monthly, both by a licensed contractor
  • local councils and public health units audit the operations of cooling towers as required
  • water service providers must provide an annual certification of disinfection to the building owner; this can be audited on inspection by the local council or public health unit.

NSW Public Health Act 2010

Under section 28-30 of the NSW Public Health Act 2010, cooling towers must be properly installed, operated and maintained.  Under section 31 of the Act, the occupier of premises must notify the local council in a timely way when a water-cooling system is installed. Under section 33 of the Act, in an outbreak of Legionnaires’ disease, the Secretary of the Ministry of Health can direct any investigation and an authorised officer may order the occupier of the premises to take actions to maintain a cooling tower.

NSW Public Health Regulation 2012

Under the NSW Public Health Regulation 2012, air-handling systems, hot-water systems, warm-water systems and water-cooling systems:

  • must be installed, operated and maintained according to Australian/New Zealand Standard:  Air-handling and water systems of buildings —Microbial control, Parts 1 to 4  (AS/NZS 3666.1-4:2011)
  • must have safe and easy access for the purpose of the cleaning, inspection and maintenance  
  • must be equipped with a disinfection procedure that is in operation at all times and that is designed to control microbial growth so that the level of Legionella in the system is not more than 10 colony-forming units per millilitre, and the heterotrophic plate count in the system is not more than 100,000 colony-forming units per millilitre. Where this is exceeded, remedial action must be taken as soon as practicable by a competent person or a person acting under the supervision of a competent person.

All tests carried out in the course of complying with the prescribed maintenance requirements for a regulated system must be carried out in a laboratory accredited by the National Association of Testing Authorities for that purpose.

The occupier of premises on which a water-cooling system is installed must:

  • ensure the system is certified annually by a competent person as being equipped with a disinfection procedure that is effective under the range of operating conditions that could ordinarily be expected for the system concerned. The occupier must keep a copy of the most recent certificate at the premises and make it available for inspection on request by an authorised officer
  • notify the local government authority within seven days of any change in the particulars provided to the authority in the approved form under section 31 of the Act.

Each local government authority must maintain a register of water-cooling systems and warm-water systems installed on premises in its area. The register must contain the following particulars relating to each regulated system:

  • the address and telephone number of the premises on which the system is installed
  • the name and contact details of the occupier of the premises (including residential address, e-mail address and home, business and mobile telephone numbers)
  • the Australian Business Number (ABN) or Australian Company Number (ACN) (if any) of the occupier of the premises
  • the type of regulated system
  • details of any inspections carried out by the local government authority for the purposes of the Act.

What causes an outbreak of Legionnaires’ disease?

Although 10 per cent or more of cooling towers may be contaminated in a city, most are never found to cause outbreaks of disease. The reason why some cooling towers are associated with outbreaks is unclear, but probably relates to a range of conditions occurring coincidentally. These are likely to include: contamination of the cooling tower; weather conditions such as the level of humidity, sunlight, temperature and wind direction, and susceptible people being located in a position where they can breathe in contaminated water vapour.  

Most people who breathe in contaminated water vapour will never get sick. The people most likely to become ill are those who smoke, have underlying illnesses and who are elderly.

Internationally, outbreaks of Legionnaires’ disease can vary in size, ranging up to hundreds of identified patients. In 2015 in New York City, 133 patients were reported with Legionnaires’ disease, 16 of whom died. In Melbourne ​in 2000, 125 patients with Legionnaires’ disease were reported in association with an outbreak linked to the Melbourne Aquarium.

What is the public health response to Legionnaires’ disease cases?

Laboratories and hospitals are required to confidentially notify cases of Legionnaires’ disease to public health units in NSW. Public health unit staff carefully interview patients or their carers about their illness and possible exposures. This often includes multiple interviews to identify all possible locations where they travelled, worked, stayed or visited during the two to 10 days before onset of illness. Public health epidemiologists then map these locations and compare them closely with the exposures reported by other patients who have recently been diagnosed with Legionnaires’ disease. 

As the bacteria that cause Legionnaires’ disease are common in the environment, it is rarely possible to know how an individual patient became infected.  However, where multiple patients are infected, public health epidemiologists search for common areas of exposure. Should multiple patients be diagnosed with the disease, then potential sources of infection can be more accurately pinpointed.  

What happens when two patients report common exposures?

Two people with the illness visiting the same place, such as a busy shopping centre, may be coincidental and does not necessarily indicate that’s where they were infected, as people may report common exposures by chance. However public health units take a precautionary approach to such reports. Where two cases report a common exposure,  public health unit staff work with local council environmental health officers to review possible sources of infection (such as cooling towers)  in the area to assess whether they may have been a risk for infection and, if necessary, require them to be cleaned.

In addition, alerts may be issued to laboratories and doctors serving the area where patients have been reported to check whether other patients may have the disease. This is called active surveillance.   Where there is no reasonable evidence that the common exposure area reported by the two cases is the location at which they were infected, public health warnings are not usually necessary. There is the risk that such warnings may have quite negative effects on the community if they inappropriately imply that a certain area was the cause of an outbreak, adversely affecting local businesses.    

What happens when three patients report common exposures?

Should active surveillance identify more than two cases reporting common exposures, then there is an increased probability that the source of infection may be in that location.  In response, public health units continue with the actions identified above and, in the absence of an alternative source, a public health media alert may be issued to raise awareness about the disease to encourage early diagnosis of other cases, and remind building owners of the need to ensure cooling towers are clean and disinfected. Additional steps including specific alerts may be issued directly to cooling tower operators.

When are deaths publically reported?

It’s tragic when somebody dies from a communicable disease. Around 10 per cent of people with Legionnaires disease die despite treatment. Deaths tend to be more common in vulnerable patients with underlying disease. However the proportion of people who die with Legionnaires disease is not related to whether or not the person acquired the infection as part of an outbreak or not. The extent and severity of an outbreak is usually measured by the number of patients who have been affected, rather than the number of deaths.

Strict privacy rules apply to the release of information about patients and it’s important that patients know their privacy is respected. Even if their name is not included, the release of other information about a patient (for example, their date of birth, sex, disease, risk factors and treating hospital) could allow other people to identify that person and infer private information about them. So when a death occurs in someone with Legionnaires’ disease, there is need for careful consideration of whether the release of that information would help protect public health, or risk breach of privacy.

How can you determine the source of an outbreak?

It is often very difficult to pinpoint the source of an outbreak with accuracy. The main aim of a public health response is to stop the outbreak continuing as soon as possible by ensuring that cooling towers and other possible sources of infection in a location suspected to be the cause of the outbreak are controlled as quickly as possible. To achieve this, building owners are warned to maintain cooling towers to ensure they are free of contamination, and environmental health officers carry out door to door inspections of cooling towers.

A cooling tower that is the source of an outbreak may not be identified despite careful investigations. This is because a cooling tower may be only transiently contaminated by Legionella bacteria floating through the air, and water vapour from that cooling tower may infect people walking by, as well as contaminate other nearby cooling towers. However that cooling tower’s continuous disinfection and regular cleaning processes may automatically decontaminate it, even before infected patients are diagnosed. Should the first cooling tower be tested, it may therefore test negative for Legionella (because it’s been automatically disinfected), even though it’s the real source of patients’ infection, while the nearby cooling towers (contaminated by the first cooling tower, but not yet disinfected) may test positive, even if they have not caused any infections in patients.

NSW Health is developing special tests (such as whole genome sequencing) that can match the strains of bacteria found in patients and in cooling towers. However even if a patient’s strain matches a cooling tower strain, it does not prove it was the source of infection, as both the patient and that cooling tower may simply have been contaminated by another cooling tower that may never be identified (e.g. because it already had been disinfected).

Page Updated: Thursday 20 July 2017