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Legionella: The hidden risk

Eric Myers, Senior Industry Technical Consultant at Ecolab and a Waterborne Pathogen Risk Reduction Strategist, on how the unique circumstances for buildings that wouldn’t typically experience months-long shutdown may have increased the risk of legionella and how to mitigate that risk

Many businesses around the world have had little to no occupancy during the COVID-19 pandemic. Low occupancy could potentially become a public health threat within commercial office buildings that have remained dormant. Many facility managers could be caught unprepared if these risks are not appropriately examined and addressed as businesses begin return-to-office plans.

One often over-looked risk is Legionella. As buildings experienced reduced occupancy during the last two years, water flow within buildings has also decreased, which can increase the risk of a Legionella growth and spread. Legionella, a waterborne pathogen, can grow in stagnant water systems. When inhaled as an aerosol or water mist, it can have severe health risks – causing symptoms similar to pneumonia, high rates of hospitalisation and increased risk to the immunocompromised. According to the CDC, one out of 10 Legionnaires’ disease cases are fatal, making it a critical risk for facility managers to address.


While many facilities have water safety management plans already in place, the last two years have presented a unique situation. Factors such as water stagnation, insufficient disinfectant and poor temperature controls can lead to conditions that allow the growth and spread of Legionella from common water access points like water fountains, sinks and showers. Cases are projected to continue increasing with urbanisation, ageing populations, and water systems. Not only can Legionella cause severe health risks, the World Health Organisation estimates an outbreak can cost an average of $10.6 million in tangible expenses like remediation and lost productivity, plus soft costs like damage to brand reputation.

Return-to-office plans should consider and address Legionella risks before building occupancy increases. The five points outlined below can help identify and mitigate the risk of Legionella in your building.

Review or develop a water management plan – Taking a water system inventory, developing process flow diagrams, and assessing risk

It is important to create a written plan for the water systems first. The plan should include identification of at-risk water systems, specification of proper operation parameters and control measures, and guidelines for maintenance. Technology such as 3D TRASAR™ Cooling Water Technology gives facility managers the platform to measure and monitor risks. Further, Water Safety Intelligence , powered by ECOLAB3D, enhances traditional water risk management by providing 24 / 7 visibility to help identify and mitigate potential risks.

Give consideration for long-term supplemental disinfection – Choosing the optimal solution

Complex water systems, lack of potable water disinfectant residuals and ideal temperatures for the growth of Legionella may drive the need for supplemental disinfection. Supplemental disinfection remains among the best strategies to limit microbial growth in a building’s domestic water system. Domestic cold and hot water systems can provide ideal conditions for pathogen growth, and system complexities can be challenging to address. However, current technology generates chlorine dioxide or chlorine onsite to help address these unique challenges and support proper control of the disinfectant application.

Point-of-use water filters can be a short-term fix

Point-of-use water filters can be used in an emergency to allow time to implement remedial action or as a long-term control strategy for high-risk of critical areas. These filters are commonly used in showers, ice machines or other water fixtures.

Implement short-term remediation procedures

Short-term remediation procedures can be performed on many types of water systems including cooling towers, potable water systems, decorative water features and potable water storage tanks. Remediation involves not only cleaning and chemical disinfection, but also providing the proper documentation to verify the process was completed. Seek the help of an experienced and competent service provider to ensure proper procedures are safely followed.

Legionella monitoring using culture and molecular testing

Molecular-based tests for Legionella identify the presence of Legionella DNA in water and provide results in genomic units within one to four-days. Monthly test results can show if Legionella bacteria are increasing and can complement quarterly Legionella culture testing to ensure the effectiveness of a water management plan. The molecular-based test can also be used to confirm the effectiveness of remedial cleaning and disinfection procedures.

With varying occupancies and operational changes, the conditions facing facility managers are unlike any we have experienced before. It is now more important than ever for facility managers to view water safety as a continuous process of assessing, acting, analysing, adjusting, and repeating. Identifying water risks is an essential step before office employees can confidently return to a new version of business-as-usual.

In association with https://en-uk.ecolab.com

About Sarah OBeirne

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