Preventing Legionnaire's Outbreaks

Amid COVID-19, remote work became the new normal, with the doors to most commercial offices closed for at least 90 days. The same was true for hotels, restaurants, theaters, gyms, factories, and other businesses that have been temporarily shut due to the pandemic. As businesses reopen, now there are also concerns about Legionnaires’ outbreaks, a potentially deadly consequence of the coronavirus.

Legionnaires’ disease is a severe, sometimes deadly respiratory condition caused by inhaling water droplets that contain the Legionella pneumophilia bacteria. The bacteria live in warm environments, surviving in biofilm – “clusters of microbial life that gather on surfaces” – and feeding on pipework sludge and sediment. Legionnaires’ disease does not spread from person to person but causes large outbreaks through contaminated airborne water droplets from sources including showerheads, taps, cooling towers, air-conditioning systems, spa pools, hot tubs, and water fountains. The disease tends to affect people with compromised immune systems, with COVID patients and survivors potentially even more vulnerable.

Building Closures Are Breeding Ground for Legionella Bacteria

The temporary shutdown or reduced operation of a building and reductions in normal water use can create hazards for returning occupants. According to the Centers for Disease Control and Prevention (CDC), for Legionella, a “prolonged period” may be weeks or months depending on plumbing-specific factors, disinfectant residuals, water heater temperature set points, water usage patterns, and preexisting Legionella colonization. The pandemic-related shutdown of businesses has led to an unprecedented amount of stagnant water in the pipes or even in individual taps and toilets in dormant buildings, potentially creating a breeding ground for Legionella bacteria.

Risk-Mitigation Measures

While larger commercial office buildings and industrial clients typically have professional maintenance staff that kept the water flowing throughout the shutdown, smaller buildings may have not taken the same precautions. Following are several measures that clients should take before they open their doors to employees, guests, and customers:

  • Ensure the water heater is properly maintained and the temperature is correctly set.
    • This may include draining the water heater after a prolonged period of unuse, based on manufacturer guidelines.
    • The water heater should be set to at least 140°F, as higher temperatures can reduce the risk of Legionella growth.
  • Flush the water system in order to replace all water inside the building piping with fresh water; flush until the hot water reaches its maximum temperature.
    • Other water-using devices, such as ice machines, may require additional cleaning steps in addition to flushing, such as discarding old ice. Follow water-using device manufacturers’ instructions.
  • Disinfect all decorative water features, such as fountains, following recommended manufacturer guidelines.
  • Hotels should ensure that all hot tubs/spas are safe for use if they make these amenities available to guests when reopening.
  • Disinfect cooling towers regularly.
    • The tower and basin should be free of visible slime, debris, and biofilm before use.
  • Ensure safety equipment including fire sprinkler systems, eyewash stations, and showers are clean and well maintained. Regularly flush, clean, and disinfect these systems according to manufacturer specifications.
  • Maintain the water system, including contacting the local water utility to learn about any recent disruptions in the water supply.
    • After the water system has returned to normal, ensure that the risk of Legionella growth is minimized by regularly checking water quality parameters such as temperature, pH, and disinfectant levels.

Stagnant plumbing systems in closed buildings could put employees and guests at risk for Legionnaires’ disease. A single small outbreak can sicken many people. It’s critical that a risk management program is in place to prevent potential outbreaks as businesses look to reopen.