Case Study: Legionella and Legionnaires’ Disease outbreak at long-term care home | AMES Legionella Control Services

Never a week goes by without the local or national media reporting on something tragic or disastrous such as the outbreak of a house fire which results in tragedy.  However rarely do the media then follow up on the reasons and causes of such an event, which limits the resulting widespread public safety, awareness or health benefits.

At AMES Legionella risk control we believe lessons can be learned from case studies of legionella and Legionnaires’ disease outbreaks, their management and we aim to look at these events in coming weeks.  This will include the outcomes, reasons for the outbreak and what has been learned in the respective countries where the outbreaks occurred, globally and industry-wide.

Legionella Outbreak Toronto 2005

One of the most serious outbreaks of Legionnaires’ disease occurred in Toronto, Canada in 2005.  The outbreak occurred in a long-term care home.  135 people in total were infected, 70 of them residents, 39 staff, 21 visitors and 5 people who worked near the home.  Twenty three residents out of the seventy infected died as a result of the outbreak.  During the first 10 days, the cause of the outbreak was not known.

One of the things that stood out in this case was the difficulty had in identifying what the outbreak was.  It was also a test of whether lessons had been learnt from the previous public health incident which was also hard to diagnose, the SARS outbreak in Ontario in 2003.

When outbreaks do occur in the province the aim is to successfully achieve two immediate goals:
1.) Provide the best possible care for people who are ill
2.) Prevent or control the spread of the infectious disease
The panel of medical experts and public health professionals found that the response did meet achieve these two goals.  Despite the loss of life it was deemed that the response to the outbreak was more organized, efficient and effective than the response to the SARS outbreak and it was clear that many of the previous learnings had been applied.  Despite that, the experts acknowledged that there were still serious flaws in the public health system which needed addressing.

The Legionnaires’ outbreak was not regarded as a large outbreak, affecting just over 100 people in a contained geographical proximity.  The situation benefitted from having the provinces largest and best equipped public health unit nearby.

If the outbreak had been more widespread or the disease more virulent it was stated that the outbreak could have had far worse consequences, with the system as it was stretched under such circumstances.  The fact that 23 deaths did occur in an outbreak considered to be relatively small and contained, highlights why HSE and ACOP L8 legislation has been put in place here in the UK, with risk control reviewed and scrutinised further since the Legionnaires’ disease outbreak in Wales in September 2010.

The importance of not cutting back on essential public health protection despite hard economic times was highlighted in ‘For The Public’s Health’ which stated that even in times of fiscal restraint, we must remind ourselves of the cost of ignoring the essentials.

The panel went onto review Ontario’s efforts to revitalize their public health system  and protect public health.

The report first reminded people of some facts on the infection itself.  Principally that people do not become ill from drinking water containing the bacteria. People inhaling mist from a water source that contains high concentrations of the bacteria can become ill with Legionnaires’ disease.  Legionella does not spread from one person to another.  Pontiac fever is the milder form of illness that most healthy people exposed to Legionella develop.  The people more likely to develop the more serious and life-threatening Legionnaires’ disease are those with a weakened immune system or underlying illness including the elderly, smokers, organ transplant patients, people taking corticosteroid therapy and those with chronic obstructive pulmonary disease. The US Centers for Disease Control and Prevention reports that most cases of Legionnaires’ Disease go unreported as it is difficult to distinguish from other forms of pneumonia.  Therefore, despite reports of between 8000 and 18000 people being hospitalized per annum in the US, the real infection rates are likely to be considerably higher.  Worldwide outbreaks have been reported which have been linked to whirlpool and hot tub spas, mist sprayers in food stores, potting soil, cooling towers and water fountains.

In 2005, the panel report suggested that febrile respiratory illnesses were fairly common in long-term care facilities for the elderly.  This was partly due to the inhabitants falling into higher risk categories and due to the fact that in closed communities infectious diseases tend to spread quite easily.

Approximately 250 – 450 outbreaks of all sorts of respiratory and non-respiratory outbreaks were believed to be handled by Toronto public health throughout the course of a year.  With outbreaks of respiratory illnesses being quite common in long term elderly care homes, it was felt that conservable effort had been made to find out about and manage these incidents.

The Legionnaires’ disease outbreak in more detail

The Seven Oaks Home for the Aged was the site of the 2005 outbreak.  The instances of illness were first noticed on 24th September when residents on two floors developed fevers; at this point staff began to follow standard procedures for an occurrence of this nature.  Patients were line listed, temperatures taken, fluids given and activities were reduced on floors where the illness had been noticed.

The number of ill residents reached a peak on September 30th.  By October 1st 2005 60 out of the 249 residents were ill, four had died with a further 17 hospitalized.  Staff had also contracted the illness 5 of them were reported ill and one had been admitted to hospital.  One visitor had also presented at hospital with symptoms.

The Central public health lab analysed specimens from residents who had been taken ill. This includes testing for common causes including influenza, RSV and parainflenza, in addition to Legionnaires’ disease.   All samples came back negative.    It was samples taken from autopsies carried out on those that had dies that actually identified the illness as being Legionnaires’ disease.  This was found to be the case on 6th October 2005.

The public health department instructed the care home to shut down its cooling and water systems. Testing of water samples commenced.  The first samples also gave negative results, at which point all cooling towers were drained and samples of this water were analysed.  It was 21st October 2005 when the tests confirmed that the cooling towers had contained the same strain of Legionella as had been found in autopsy specimens.  The cooling towers linked to three nearby buildings were also found to contain the same Legionella strain.  Despite this the high attack rate within the Seven Oaks Care home and the fact that all cases were connected to the building suggested that the release of Legionella from the Seven Oaks cooling tower was the probable cause of the outbreak.

By this point cases subsided, leaving 23 residents dead and 135 people in total having become ill, in all likelihood from the same one cooling tower.

When Legionnaires’ disease breaks out the goal is to treat those who have become ill and crucially find the source.  All people were likely infected during a 4 – 5 day infection window, after which point no others were infected. However, until the cause and pattern of this illness is identified, the response to the outbreak has to assume that there is an on-going problem, leading to continued measures to stop the spread of the disease.

The response to an outbreak such as the one in Toronto involves many organizations, including hospitals, emergency health services, the Chief coroners office, the cities public health department, central public health laboratories and community health (including the care home effected itself).

Experts concluded that in many ways the response to the Legionella outbreak in this case was textbook.  Weaknesses did however focus on the availability of hospital resources (beds) and on arrangements for transfers to hospital, the availability of people, skills and expertise (i.e. the capacity to cope with a surge in demand); equipment and infrastructure and information systems and communication.

The panel found that the uncertainty of the cause of the illness coupled with the frail nature of ill residents made caring for the patients particularly stressful.  Nevertheless they found that the patients received excellent care both at the care home and in hospital.  Care home workers responded admirably to the increased challenges and physicians were on call 24 hours a day. 19 additional staff were brought in by the care home.  They continued to provide thorough care even after the water system had to be turned off.

The panel also concluded that it would not have been possible in this case to prevent any of the deaths.  Residents achieved timely and appropriate levels and types of care, despite the initial diagnosis being uncertain.  The delay in diagnosis caused alarm and concern for all involved but did not adversely affect the treatment or care received by residents, staff or visitors who became ill.  Those who died had complex underlying conditions, and any other medical treatment could not have prevented their death.

More Recent Follow Up

More recently, in May 2011, the Ontario Public Health Agency produced a presentation reviewing the outbreak and progress in the field of diagnosing and controlling legionella and Legionnaires’ disease outbreaks.  It was presented by the Infection Control Consultant.

It initially briefly covered the history of Legionnaires’ disease, from its first identification in 1976 at the American Legion convention at the Bellevue-Stratford Hotel in Philadelphia, which gave rise to the name Legionnaires’ disease.  In this first identified outbreak 221 cases were reported, resulting in 34 deaths.  In this first case of Legionnaires’ disease the outbreak had been caused by the cooling tower linked to the hotels air conditioning system.

The presentation also looked at Pontiac disease, the illness which tends to be suffered by less vulnerable people when exposed to legionella.

Outbreaks have been reported on cruise ships, in hotels and resorts, office buildings and factories as well as numerous care facilities around the world.

What is Legionella?

Legionella is an aerobic, gram negative bacteria. There are 46 species and 68 sero-groups.  The most common is Legionella pneumphilia, which is responsible for 0% of human infections.

Legionella Pneumophilia

Legionella pneumophilia is present in soil and both man-made and natural water environments.

Lakes, rivers and streams have a bio-film or slime on the surface in which the bacteria grows.   As this type of Legionella can tolerate chlorine, it will survive in drinking water systems, although it grows particularly well in stagnant warm water.  Temperatures of 24-42 degrees C are particularly beneficial to the growth of the bacteria.   Infection of humans occurs when aerosolized, contaminated water is inhaled.

Cooling towers were highlighted to be particularly prone to the risk of legionella outbreak due to the way in which they operate – cooling water through direct contact between the water contained and a stream of air.

Food retail store mist producers and potable water distribution systems were also identified as risk factors, along with hot tubs, decorative fountains and shower heads.

The severity of illness as a result of Legionnaires’ disease can vary from a mild cough to low fever, through to rapidly progressing pneumonia and coma – particularly in high risk groups.

The Ontario public health agency presented that the incubation period for the disease is 2 – 10 days.

Early symptoms includes malaise, muscle ache and mild headache.  Fatality rates were reported as up to 50% of hospitalized patients, with up to 30% of community acquired cases proving to be fatal.

The presentation also reinforced that problems continued with diagnosing the type of pneumonia as actually being Legionella-related. As most pneumonia is treated empirically, the causative agent is never identified in many cases.  Episodes of cases attributable to Legionella in Ontario in 2010 studies was found to be 7574 cases, in which 59 resulted in death of the patient.

The fact that estimates of US hospitalizations due to Legionnaires’ disease varied from 8000 to 180000 demonstrated how difficult it is to tell the illness from other types of pneumonia, with most cases going unreported.  They found that performing more than one test increases the likelihood that  they would confirm Legionella.  Methods of testing available included isolating Legionella form sputum or tissue and detecting antibodies in urine.

As no test was found to be 100% sensitive inevitably negative test results did not guarantee that infection was not present.  Treatment with standard antibiotics was normally found to be successful. Penicillin, cephalosporins and aminoglycosides was found not to be effective.

What preventative lessons were learned from the Ontario outbreak?

Key measures found to prevent Legionella included:

  • Draining cooling towers when they were not being used
  • Periodic cleaning should be done to remove sediment and scale
  • Cooling towers and evaporative condensers should be subject to inspection and thorough cleaning, minimum of once a year
  • Biocides used in cooling tower water were found to assist
  • Making sure air intakes were not near water in cooling towers
  • Hot water to be maintained at above 50 degrees
  • Tap water should not be used in respiratory therapy devices

The presentation also raised examples of instances of Legionella at the Playboy Mansion hot tub, vacation resort Cozumel Mexico in December 2010 – January 2011, and also in South Wales in October 2010.  We will review these cases of Legionella and Legionnaires’ disease outbreaks separately.



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