Legionella risks emerging from lockdown

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As buildings are reopened, businesses must manage the risks from legionella bacteria in water systems.

It has been widely reported that buildings being reopened following the Covid-19 lockdown have the potential for a greatly increased risk of Legionnaires’ disease due to water stagnation and absence of normal control measures.

What is Legionnaires’ disease?

  • Legionnaires’ disease is a potentially fatal pneumonia caused by inhalation of legionella bacteria in a water aerosol
  • The disease kills around 7-12 per cent of those infected in the normal population, according to Public Health England statistics
  • Mortality rates in hospital-acquired Legionnaires’ disease infections are far higher
  • Legionnaires’ disease from building water systems is preventable.

Failure to manage water systems can lead to prosecution with large fines or imprisonment for those responsible such as employers or those in control of premises.

It is recognised that Legionnaires’ disease is already under-reported in the UK. It is often simply classed as pneumonia without identification of the causative agent. Despite 503 confirmed cases of Legionnaires’ disease in 2019 (according to Public Health England), research has estimated that 4,000-6,000 cases of Legionnaires’ disease occur every year in the UK.

Covid-19 has very similar symptoms to Legionnaires’ disease and Covid-19 fatality is often as a result of a secondary pneumonia, according to recent research. There is evidence emerging that this secondary pneumonia could be Legionnaire’s disease in a significant percentage of cases.

The Legionella Control Association (LCA) has received numerous enquiries around legionella control during the Covid-19 lockdown and has received feedback from our members involved in legionella control. Some of these experiences are discussed below to give some examples and lessons that others can learn from and therefore reduce the risk of Legionnaires’ disease.

What needs to be done during Covid-19 to control legionella risks?

The HSE will still enforce breaches of health and safety law during Covid-19 and the legal requirements for legionella control have not changed. These are to assess the risk and take appropriate measures to eliminate or control the risk as far as reasonably practicable.

A summary of the legal obligations and available guidance can be found
on the LCA website.

All buildings with water systems should already have a legionella risk assessment in place and a legionella written scheme of control that documents how the water systems are managed safely. The challenge from Covid-19 was that the unexpected nature of the lockdown was not reasonably foreseeable and therefore not included in most existing control schemes.

Many plans had to be made at short notice, with limited resources and the shutdown of buildings may have been done without consideration of the legionella risks leading to conditions which are favourable for growth of legionella bacteria.

We received reports early in the lockdown that site managers were turning away contractors involved in critical legionella control work, such as evaporative cooling systems treatment. The message from the LCA to our members, in consultation with our HSE and local authority environmental health officer colleagues, was where a high risk system such as this was being neglected, use the LCA escalation procedure and report to the relevant enforcement agency if necessary.

What needs to be done to minimise legionella risk when reopening buildings?

We have been asked by building managers and LCA members for the specific steps required to safely recommission the water system in a building. There is no ‘one size fits all’ answer to this. However, the process will generally involve:

  • Understanding the legionella risks
  • Consideration of control measures (flushing, cleaning, disinfection, etc.)
  • Consideration of validation strategies to demonstrate the control measures have been effective (inspection, sampling, temperature monitoring, biocide residuals, etc).

We have issued guidance for our members regarding the recommissioning process and what to consider, and this can be found on our website. The guidance is designed to help with the risk assessment process, but it does not replace it.

Understand the legionella risks

The process must be based on specific assessment of risk and review of the existing risk assessment and written scheme of control.

Control measure considerations

Buildings left idle without simulation of use will require some intervention to make their water system safe prior to reopening. The degree of intervention is the decision of the duty holder but our advice has to be, if it is not possible to reopen safely; do not reopen.

Many buildings being reopened are undergoing disinfection and flushing of their water systems prior to the system being used. This work must be completed by competent operatives and the LCA directory lists audited specialist contractors. There is good guidance on how to recommission water systems in HSE’s booklet, Legionnaires’ disease Part 2: The control of legionella bacteria in hot and cold water systems (HSG274) and the BSI Standard, BSI PD 855468:2015 Guide to the flushing and disinfection of services supplying water for domestic use within buildings and their curtilages.

After a period of prolonged stagnation it is possible for a single disinfection to be ineffective and the process may need to be repeated. We do have reports of some unsuccessful disinfection processes –  i.e. the system tests positive for legionella after the work is complete. This highlights the need for a validation process to confirm the effectiveness of the control measure.

Validation considerations

Validation is defined as written evidence of the checks and monitoring required to establish that the control measures have been effective. This may include inspection, sampling, temperature monitoring, biocide residuals, etc.

Sampling for legionella can be a key part of reopening buildings provided it can validate the control measures that have taken place. However, Legionnaires’ disease has been attributed to at least 20 species of legionella so sampling should look for all species and not concentrate on just Legionella pneumophila, as is sometimes done.

We have received queries on sample results where it appears a duty holder has taken water samples from their own building, got back a legionella result and do not know what it means.

If you are not competent to interpret the results of sampling, we advise the use of a competent contractor such as an LCA member.

Do we expect more cases of Legionnaires’ disease?

We hope not; but given that Legionnaires’ disease symptoms are so similar to Covid-19, the situation may not be clear for some time. Increased awareness of susceptibility to Legionnaires’ disease (prompted by awareness of the largely  similar Covid-19 susceptibility) means that duty holders may have to adjust their longer term view of Legionnaires’ disease risk as new information emerges about their building users.

There is potential for an increase in Legionnaires’ disease deaths and serious long term health implications. If you are an employer or in control of premises you should be aware of the legionella risks in your building, the controls in place to keep your occupants safe and to avoid the associated prosecutions and litigation.

The LCA has nearly 400 audited members who have in place documented processes to ensure the competence of their staff in delivering specialist legionella control services. We have published a buyer’s guide to assist service users in choosing a suitable contractor for legionella control work.

The LCA is a non-profit membership organisation committed to raising standards in legionella control. We publish a code of conduct and standards for service delivery that our members are audited against. A key commitment of LCA membership is maintaining the competence of employees.

For more details see: www.legionellacontrol.org.uk

Matt Morse is manager at the Legionella Control Association



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