Cutting the risk of Legionnaires’ disease from shuttered water systems

Legionella pneumophila
Illustration of Legionella pneumophila, the bacterium that causes the majority of Legionnaires’ disease cases and outbreaks. Credit: Centres for Disease Control and Prevention

By Jay Whiteside

Legionella, the bacterium that causes Legionnaires’ disease, grows very easily in the standing water of building water systems. Legionnaires’ disease is potentially lethal, and its incidence is increasing. Often, however, it is misdiagnosed as community-acquired pneumonia in up to 50% of cases, and is underdiagnosed by as much as a third of its actual incidence.

If a school, church or other type of building has been minimally utilized during the COVID-19 shutdown, a water system or any devices that utilize water are at risk as a breeding ground for Legionella. This includes faucets, soda fountains, water lines to ice makers and coffee machines, ornamental fountains, HVAC cooling towers, showers, hot tubs/spas, eyewash stations, fire sprinkler systems, and plumbing in general.

In the post-COVID lockdown, building water systems can present a greater risk to public health than before. Evidence from China indicates that half of COVID-19 fatalities had experienced a secondary infection and patients are at elevated risk for months after recovery.

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The continued growth of Legionnaires’ disease is the result of the lack of a water management plan and other factors such as:

Environmental: Aging population; aging water infrastructure; extreme weather fluctuations; heavily populated regional concentrations (i.e., mid-Atlantic and Great Lakes); new energy conservation measures in buildings.

Epidemiological: Underreported; misdiagnosed; mistaken.

Liability issues

There are notable liability issues as a result of the increase in Legionnaires’ disease. While the legal landscape is aligning around the concept of Standard of Care, building safety is still underregulated so building managers tend to ignore their water systems. Before ASHRAE 188 (2015) courts would throw out Legionella claims, because there was no industry benchmark on which to base a standard.

With the broad public consultation that preceded ASHRAE, and the increasing incidence of cases, it has become easier for plaintiffs’ lawyers to argue negligence in meeting a Standard of Care. However, litigation is increasing and taking on the character of slip-and-fall accidents. The majority of civil suits end in confidential pre-trial settlements.

There are some notable benchmarks, including a 2014 class action precedent in Canada (successfully prosecuted against Seven Oaks Nursing Home, Toronto, Ontario) and criminal charges against 15 state and city officials regarding the Legionella outbreak in Flint, Michigan.

Insurance underwriters weigh in

Insurers have a lot to lose and face an increasingly urgent mandate to mitigate the risks in their clients’ buildings and facilities. Frequently, Legionella claims generate discussion as to whether Commercial General Liability coverage is sufficient for claims caused by microorganisms and a broad definition of pollutants. It is suggested that an Environmental Impairment Liability policy be purchased for these emerging contaminants. Recently, some insurance companies have attempted to deny coverage based on policy exclusions and dispute over what constitutes “bodily injury.”

A successful defence against litigation or denial of insurance coverage includes a clear strategy to protect the building from being colonized by Legionella (i.e., a water management plan, with identified “‘potential exposure points” based on a risk assessment).

The ”best insurance” is to implement control measures that minimize the growth of Legionella bacteria. A regular maintenance program that quantitatively monitors the building’s water systems should include checks of water disinfection residuals and temperatures, scheduled water system flushes, and comprehensive reporting and documentation.

Risk assessment

Current risk assessment methods look for Legionella specifically but often find false negatives since the Legionella bacteria can be hidden in biofilm. SanEcoTec has developed SMART (Self Monitoring Analysis Reporting Technology), which analyzes water quality in real time and to check biofilm and other parameters in plumbing systems where Legionella bacteria are harboured and then released at infectious concentrations.

Occasional checking of disinfectant residuals or water temperatures alone is no guarantee Legionella bacteria won’t release from the existing biofilm that harbours them. An integrated approach that includes a comprehensive risk management plan with ongoing monitoring can help manage and prevent potential problems.

Jay Whiteside is with SanEcoTec Ltd. Email: (References are available upon request.)

Read the full article in ES&E Magazine’s August/September 2020 issue:

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