Advice about Legionella risks

Legionella risks during the coronavirus outbreak

Legionnaires’ disease is a type of pneumonia which can cause serious illness in persons who are susceptible such as those over 50 years, smokers, and those with underlying health conditions.

The disease is caused by the growth of Legionella in building water systems which are not adequately managed. Closure of buildings, parts of buildings or their restricted use, can increase the risk for Legionella growth in water systems and associated equipment including evaporative air conditioning systems and other equipment if they are not managed adequately. [1]

If your building was closed or has reduced occupancy during the coronavirus (COVID-19) outbreak, water system stagnation can occur due to lack of use, increasing the risks of Legionnaires’ disease.

You should review your risk assessment and manage the legionella risks when you:

  • reinstate a water system or start using it again
  • restart some types of air conditioning units

If the water system is still used regularly, maintain the appropriate measures to prevent legionella growth.[2]

Where to start

  • Review and update your risk assessment and document how you will protect staff, visitors and others from Legionella growth who remain on your property and when it is re-opened.
  • Get advice from an experienced water treatment advisor, public health or environmental health authorities.
  • Check your local Council’s advice on Legionella
  • Where national guidelines or legislation are in place then you must follow those.

Flushing and Restarting Systems

  • Be aware that the procedures you will need to follow to safely flush and restart your water system varies depending on how your water systems were managed during closure.
  • For information on safely flushing and restarting your water system, please download the full guidance on managing Legionella in building water systems created by the European Society of Clinical Microbiology and Infections Diseases (ESGLI).


[1] ESGLI Guidance for Managing Legionella in Building Water Systems during the Covid-19 Pandemic, 2020

[2] HSE advice on the risks of legionella during Covid-19 outbreak, 2020


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