Employers, the self-employed and people in control of premises, such as landlords, have a duty to protect people by identifying and controlling risks associated with legionella. 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.
To read the full guidance: https://www.hse.gov.uk/coronavirus/legionella-risks-during-coronavirus-outbreak.htm