Last reviewed 25 September 2020

The Health and Safety Executive (HSE) has urged employers to keep legionella risks under control during the coronavirus pandemic, following a recent outbreak of the disease in the Midlands.

If buildings are closed or have reduced occupancy during the coronavirus pandemic, water system stagnation can occur due to lack of use, increasing the risks of Legionnaires’ disease.

Employers are advised to review their risk assessment and manage the legionella risks whenever they reinstate or start using a water system again (such as a cooling tower, evaporative condenser, spa pool, hot tub or hot showers, for example).

They will also need to review the risk assessment for legionella when they restart some types of air conditioning units. For example, some units have a source of water that can generate aerosol, so employers will need to assess the risks of legionella being present within them before restarting.

(The HSE says small wall or ceiling-mounted units with closed cooling systems should not present a risk. However, larger units may present a risk if they have improperly drained condensate trays, or humidifier or evaporative cooling sections where water can stagnate, becoming a reservoir for bacteria to grow.)

When reviewing the risk assessment, it is important to decide what the risks are for the particular units and if they need to be cleaned safely, before they are turned on.

If the water system is still being used regularly, it will be a case of maintaining the appropriate measures to prevent legionella growth.

At the time of writing, six people are receiving hospital treatment for suspected Legionnaires' disease linked to a recent outbreak in the Midlands. Public Health England is currently taking detailed histories of the patients since evidence points to the possibility of a common source. Full details are not as yet publicly available since the investigation is ongoing.

For advice on guidance on managing the risks, see the Legionnaires’ Disease topic.