Risks of the respiratory infection caused by COVID-19 are concerning, real and very much on public radar. What is less known is the increased risk of Legionnaires Disease that idle and vacant buildings are creating.

As schools, stores, hotels and businesses reopen, Legionella bacteria – known to cause the pneumonia-like respiratory ailment Legionnaires Disease – may await. Legionella bacteria grows in warm, stagnant water; water systems shut down due to COVID-19 – such as those in vacant buildings – making unused showers, cooling towers, decorative water fountains, hot tubs and plumbing systems a fertile breeding ground for Legionella. Infection occurs when someone inhales water droplets containing the bacteria.

From businesses reopening to colleges resuming classes, an awareness of Legionnaires Disease – and how to safely restart operations without spreading bacteria – is important.

  1. Develop a comprehensive water management program for your water system and all devices that use water.
  2. Ensure your water heater is properly maintained and the temperature is correctly set.
  3. Flush your water system.
  4. Clean all decorative water features, such as fountains.
  5. Ensure hot tubs and spas are safe for use, checking guidelines from local or state regulatory agencies; ensuring they are free of visible slime or biofilm before filling with water; and performing disinfection procedures before use.
  6. Ensure cooling towers are clean and well-maintained.
  7. Ensure safety equipment including fire sprinkler systems, eye wash stations and safety showers are clean and well-maintained.
  8. Maintain your water system and regularly check water quality parameters such as temperature, pH, and disinfectant levels.

The Centers for Disease Control has many resources to help you understand and combat the causes of Legionella and Legionnaires Disease. Visit, then search Legionnaires to learn how and where the bacteria grows, its harmful effects and how to minimize and prevent its growth in water systems.

Please contact your local independent agent if you have questions or concerns you would like to discuss with your Cincinnati Insurance loss control representative before your business or building reopens after a shutdown.

Our loss control service is advisory only. We assume no responsibility for management or control of customer loss control activities or for implementation of recommended corrective measures. These materials were gathered from trade services and public information. We have not tried to identify all exposures. We do not warrant that this information is consistent with Cincinnati underwriting guidelines or with any federal, state or local law, regulation or ordinance.

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