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Legionella & COVID-19

Updated: Jan 5, 2022

As another waive of coronavirus hits we look at the risks that low occupancy in buildings causes when it comes to Legionella bacteria and Legionnaires' disease.

Just when many businesses were asking employees to come back into the office a new variant of COVID-19 has hit (Omicron) the UK causing companies to again ask employees to work from home. Unfortunately the beginning of 2022 is feeling the same as last year and the prospects of another lockdown seem highly likely.

Legionella bacteria

When closing a premises many people may think that it's 'lights out and lock the doors' and all will be well however in my industry we look at the water hygiene aspect and how long periods of buildings be unoccupied has an affect on the quality of the water. There are three main things that really encourage Legionella bacteria:

  • Stagnation (water that doesn't move)

  • Nutrient (food source for bacteria i.e. scale)

  • Warm water

These 3 elements do not all need to be present for Legionella bacteria to cause a problem so if only one existed, the bacteria can still thrive.

During the first major lockdown back in 2020 many buildings became empty for long periods of time and so my task was to speak to these businesses and discuss a plan to ensure that the water was safe when people could eventually return to the building. The initial plan was to:

  • Review the risk assessment

  • Update the written scheme of control and implement additional tasks i.e. weekly flushing of low use water outlets

  • Sample for bacteria

  • Recommission the water systems if required i.e. disinfection and flushing of the entire system

By following a shutdown and reopening programme you were following the advice given by the HSE ( and also doing everything that was reasonably practicable to ensure that the water was safe to use once the building was back in use.

Legionella Risk Assessment Review

The risk assessment should be reviewed as the building water usage would change following a shutdown or a significant reduction in personnel using the water system. A review should also be carried out if one of the following is relevant:

  • a change to the use of the building where the system is installed;

  • new information available about risks or control measures;

  • the results of checks indicating that control measures are no longer effective;

  • changes to key personnel;

  • a case of legionnaires’ disease/legionellosis associated with the system.

Once the review of the risk assessment has been completed the written scheme of control should be updated and implemented.

If no Legionella Risk Assessment has been completed before then one should be done immediately.

Legionnaires' disease and COVID-19

The affects from restrictions due to COVID-19 and how this impacts the risks associated to Legionella bacteria should be recognised. We know that COVID-19 causes respiratory problems typically in older people. Legionella bacteria is similar in that it affects the respiratory system older people too.

Anyone can catch Legionnaires' disease in the same way anyone can catch COVID-19 but having an weakened immune system from having one or the other is a concern and so the risks for both COVID-19 and Legionella should be equally considered when it comes to you companies health and safety obligations.

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