Legionella rarely makes the headlines until someone becomes seriously ill.
For those responsible for buildings, water systems, health and safety, property management or compliance, however, Legionella should never be treated as a subject that only matters when there is an outbreak.
The latest published surveillance figures provide a useful opportunity to step back and consider the current picture.
In England and Wales, 472 cases of legionellosis were reported in 2024, representing a 22% decrease compared with 2023. Of these, 463 were confirmed cases of Legionnaires’ disease, with the remainder comprising cases of non-pneumonic legionellosis and Pontiac fever. The estimated incidence of Legionnaires’ disease was 0.7 cases per 100,000 population.
Scotland presents a rather different picture. Public Health Scotland reported 57 cases of Legionnaires’ disease in 2024, an increase of 7.5% from the 53 cases reported in 2023. This represented an incidence of 10.4 cases per million population and continued an increasing trend since 2021.
These figures need to be interpreted carefully. There is no single published UK-wide annual surveillance figure that can simply be produced by adding the different national datasets together, and the surveillance arrangements differ between the UK nations.
Nevertheless, the overall message for those responsible for water systems is clear:
A reduction in cases does not mean that Legionella risk has disappeared.
For facilities managers, landlords, employers, building owners and health and safety professionals, the statistics should instead prompt a more fundamental question:
Are the systems we have in place genuinely controlling the risk, or are we simply demonstrating that we have completed the paperwork?
What are the latest Legionella figures?
The UK surveillance picture is best considered by nation.
England and Wales
The latest UK Health Security Agency annual report, covering cases with symptom onset during 2024, recorded 472 cases of legionellosis among residents of England and Wales.
This was a reduction of 22% compared with 2023 and brought the number of cases broadly back towards the levels seen in 2021 and 2022.
Of the 472 cases:
- 463 were confirmed cases of Legionnaires’ disease
- 8 were cases of non-pneumonic legionellosis
- 1 was a case of Pontiac fever
The estimated incidence of Legionnaires’ disease was 0.7 cases per 100,000 population, compared with 1.0 per 100,000 in 2023.
There were also important demographic differences.
63.9% of cases occurred in people aged 60 or over, while 68% of cases were male. The estimated case fatality rate for Legionnaires’ disease was 2.8%.
These statistics demonstrate an important characteristic of Legionnaires’ disease: although everyone is potentially susceptible, the consequences can be particularly serious for people with recognised risk factors.
Scotland
The Scottish data deserve particular attention.
Public Health Scotland reported 57 cases in 2024, compared with 53 in 2023. This represented a 7.5% increase and continued an upward trend in reported cases since 2021.
The Scottish report recorded an incidence of 10.4 cases per million population.
It also reported six deaths and a case fatality rate of 10.5%.
The difference between the England and Wales and Scottish figures reinforces why it is unhelpful to look at a single headline number and conclude that the risk is either increasing or decreasing across the whole of the UK.
The underlying epidemiology is more complicated.
And for those responsible for individual buildings, national averages only tell part of the story anyway.
Why the headline reduction should not lead to complacency
A 22% reduction in reported cases in England and Wales is clearly positive.
However, it would be a mistake to interpret this as evidence that Legionella is becoming an insignificant workplace or property-management issue.
Legionnaires’ disease is a potentially fatal form of pneumonia caused by exposure to Legionella bacteria. People become infected primarily by inhaling contaminated aerosols generated from water systems or other sources.
The critical point for building managers is that the disease is preventable in many circumstances through effective management of water systems.
That means the most important question is not simply:
“How many cases were recorded last year?”
It is:
“What is happening inside the water systems under my control?”
A national reduction in cases does not tell a facilities manager whether their own building has:
- stagnant sections of pipework;
- inappropriate temperatures;
- poor circulation;
- redundant outlets;
- low-use showers;
- poorly maintained storage tanks;
- inadequate system information;
- ineffective flushing arrangements;
- poorly controlled thermostatic mixing valves;
- insufficient monitoring;
- inadequate maintenance;
- or an outdated risk assessment.
Those risks exist at building level.
Legionella is fundamentally a water-system management issue
Legionella bacteria can exist naturally in water environments.
The problem arises when conditions within man-made water systems allow the bacteria to multiply and create an opportunity for people to be exposed.
This is why effective Legionella management is not simply a matter of arranging an annual water sample.
Sampling can provide useful information, but it is only one component of a wider control strategy.
The Health and Safety Executive’s L8 Approved Code of Practice and guidance sets out the framework for managing Legionella risks. It is aimed at dutyholders including employers, people in control of premises and those with health and safety responsibilities.
The approach includes:
- identifying and assessing sources of risk;
- implementing an appropriate scheme to prevent or control that risk;
- managing and monitoring the precautions;
- keeping appropriate records;
- appointing a competent person, commonly referred to as the responsible person; and
- regularly reviewing the effectiveness of control measures.
This is important because Legionella control is not a one-off activity.
It is a management process.
The risk assessment is the starting point — not the end point
One of the most common misconceptions about Legionella management is that having a risk assessment means the risk has been dealt with.
It does not.
A risk assessment is only useful if it accurately reflects the building and its water systems and is translated into effective control measures.
The HSE states that where a significant risk is identified, a written control scheme should be established to describe the controls required to manage that risk.
That distinction is crucial.
A building may have a beautifully presented Legionella risk assessment that was professionally prepared.
But if the building has subsequently undergone:
- refurbishment;
- changes to occupancy;
- changes in use;
- changes to the hot-water system;
- alterations to pipework;
- installation of new showers;
- closure of areas;
- periods of low occupancy;
- changes in maintenance contractors;
- or alterations to water-storage arrangements,
then the original assessment may no longer accurately represent the system.
A risk assessment is therefore not something that should simply be filed away and forgotten.
It needs to remain relevant to the actual building.
The importance of the “responsible person”
Effective Legionella management requires clear accountability.
The HSE states that employers and people in control of premises must appoint someone competent to help meet their health and safety duties and take responsibility for controlling identified Legionella risks.
This person is commonly known as the responsible person.
But appointing someone is not enough.
The individual needs appropriate authority, competence, knowledge and experience relevant to the systems they are responsible for.
This raises an important question for organisations:
Does your responsible person actually have the authority and resources required to control the risk?
For example, if the responsible person identifies a problem with a water system but cannot obtain approval for remedial work, cannot stop the use of an affected outlet, or cannot require a contractor to address a deficiency, then responsibility may exist on paper without effective control existing in practice.
Good governance therefore requires more than assigning a name to a role.
There needs to be a functioning chain of responsibility.
Monitoring temperatures: evidence of control, not just a routine exercise
Temperature control is an important element of Legionella management in many hot and cold water systems.
HSE guidance indicates that, where temperature is being used as a control measure, hot water should generally be stored at above 60°C, with hot water distribution maintained above 50°C; cold water should also be managed appropriately.
The precise control strategy should always reflect the specific system and risk assessment.
What matters from a management perspective is that monitoring should not become a purely administrative task.
Consider a simple example.
A facilities team records water temperatures every week.
All the boxes are completed.
The records look excellent.
But if temperatures have gradually deteriorated over several months and nobody is reviewing the data, then the organisation may have extensive records but little effective control.
This is why trend analysis matters.
A good system should allow the responsible person to identify:
- recurring low temperatures;
- deteriorating performance;
- particular outlets that repeatedly fall outside expected parameters;
- areas affected by low usage;
- problems associated with plant or circulation;
- and failures that may indicate a wider systemic problem.
The question should not simply be:
“Have we taken the reading?”
It should be:
“What does the reading tell us about the condition and performance of the system?”
Water stagnation and low-use outlets
One of the practical challenges facing many modern buildings is changing occupancy.
Offices, hotels, residential buildings, healthcare premises, educational establishments and other properties can all experience periods where water demand changes significantly.
Unused or infrequently used outlets can create additional management challenges.
This is particularly relevant where buildings have:
- vacant rooms;
- closed floors;
- seasonal accommodation;
- rarely used showers;
- little-used welfare facilities;
- redundant outlets;
- or sections of pipework that no longer serve their original purpose.
The important issue is not simply whether an outlet is present.
It is whether the water system has been designed, operated and maintained in a way that controls the associated risk.
This is one reason why facilities managers should consider whether changes in building use have created risks that were not present when the original system was designed or assessed.
Sampling is not a substitute for control
Another common misconception is that regular Legionella sampling automatically demonstrates that a water system is safe.
It does not.
Sampling can be an important part of a risk-based monitoring strategy, but a negative sample does not mean that a system can be considered permanently free from risk.
Equally, a positive result needs to be interpreted within the context of the wider system.
The HSE provides specific guidance on when and how water systems should be tested and monitored.
The key principle is that sampling should form part of an overall risk-management approach.
It should not become the sole measure of whether an organisation believes it is controlling Legionella.
A competent approach considers the whole system:
Design → risk assessment → control measures → monitoring → maintenance → review → corrective action.
The role of competence
Legionella management can look deceptively straightforward.
Take some temperatures.
Flush some outlets.
Arrange a sample.
Complete a checklist.
File the paperwork.
But effective management requires an understanding of the system itself.
HSE’s guidance emphasises the importance of competence and clearly defined responsibilities.
This becomes particularly important where organisations outsource Legionella management.
Using a specialist contractor can be an effective approach, but outsourcing the task does not necessarily mean outsourcing the duty.
The dutyholder still needs to understand:
- what has been contracted;
- what has not been contracted;
- who is responsible for reviewing results;
- who authorises remedial action;
- who updates the risk assessment;
- who verifies that corrective actions have been completed;
- and who has overall responsibility for the building.
A contractor can provide technical expertise.
They cannot replace organisational accountability.
What landlords need to understand
Landlords have particular considerations.
The HSE notes that the risk from hot and cold water systems in most typical domestic settings is generally considered low where there is regular water usage and turnover. However, the risk assessment must consider the actual property and circumstances.
This distinction matters.
Not every domestic property requires the same level of Legionella management.
But landlords and property managers should not assume that “residential” automatically means “no risk”.
Consider properties with:
- communal water systems;
- stored hot water;
- large buildings;
- shared facilities;
- care-related accommodation;
- vulnerable occupants;
- long periods of vacancy;
- complex distribution systems;
- or unusual water arrangements.
The appropriate approach should be determined by the characteristics of the system and the people who may be exposed.
Facilities managers: where operational control meets compliance
For facilities managers, Legionella is an excellent example of why compliance cannot be separated from day-to-day building operations.
A water system is not static.
Buildings change.
Occupants change.
Usage patterns change.
Plant fails.
Valves are replaced.
Pipework is altered.
Rooms are taken out of service.
Contractors change.
Maintenance budgets change.
And every one of these factors can potentially affect the risk profile.
This is why Legionella management should be integrated into the wider facilities-management process.
For example, a refurbishment project should not simply consider architectural and mechanical changes.
It should ask:
What effect will these changes have on the water system and Legionella risk?
Likewise, when a building area is closed, the question should not simply be:
“How do we secure the room?”
It should also be:
“What happens to the water system serving that room while it is unoccupied?”
These questions turn Legionella management from a periodic compliance activity into an active part of building management.
Why “the paperwork is complete” is not enough
Perhaps the most important lesson from the latest statistics is that Legionella control should be judged by effectiveness rather than volume of documentation.
It is possible to have:
- a current risk assessment;
- a written control scheme;
- temperature records;
- flushing records;
- sampling reports;
- contractor certificates;
- maintenance records;
- training certificates;
and still have an inadequately controlled system.
Why?
Because documentation describes what should be happening.
It does not necessarily prove what is happening.
The real test is whether the control measures are appropriate, implemented and effective.
This is why HSE guidance places emphasis on managing, monitoring and reviewing precautions rather than simply creating them.
What should dutyholders be asking now?
The latest figures provide a useful trigger for a Legionella management review.
For facilities managers, landlords and health and safety professionals, the following questions are worth asking.
1. Is our risk assessment still accurate?
Has the building changed since it was completed?
Have any water systems, outlets, plant or occupancy arrangements changed?
2. Who is the responsible person?
Is the appointment formally documented?
Does the individual have the competence, authority and resources required?
3. Do we have a meaningful written control scheme?
Does it reflect the actual system?
Or is it simply a generic document?
4. Are our control measures working?
Are temperatures where they should be?
Are outlets being used or appropriately managed?
Are maintenance activities actually achieving their intended purpose?
5. Are we reviewing the data?
Who looks at temperature records?
Who reviews sampling results?
Who identifies trends?
Who decides what happens when results are outside expectations?
6. Have there been periods of low occupancy?
Were appropriate measures taken when parts of the building were unused?
7. Has the water system changed?
Have refurbishments, extensions, plant replacement or alterations affected the risk profile?
8. Are contractors being effectively managed?
Do contracts clearly define responsibilities?
Are contractors competent?
Are their reports being reviewed rather than simply filed?
9. Is there a clear escalation process?
If a control measure fails, does everyone know who needs to be informed and what action needs to be taken?
10. When was the last genuine review?
Not simply the last time a document was signed.
The last time someone critically challenged whether the whole management system was actually working.
What the latest figures really tell us
It would be easy to look at the England and Wales data and conclude that Legionella is becoming less of a concern.
The 22% reduction in reported legionellosis cases is encouraging.
But the Scottish figures demonstrate why the broader picture needs careful interpretation.
More importantly, neither national dataset can tell a dutyholder whether their own building is being effectively managed.
That remains a site-specific question.
The latest figures therefore should not trigger complacency.
They should trigger scrutiny.
The people responsible for buildings should be asking whether their water systems are being managed proactively, whether their responsible persons are genuinely competent and empowered, whether control measures are effective, and whether the organisation can demonstrate that it understands the risks associated with its particular system.
Legionnaires’ disease remains a potentially fatal illness, and HSE guidance continues to place clear expectations on those with responsibility for premises and water systems.
The objective should never be to produce impressive paperwork.
The objective is to control the risk.
Conclusion: compliance should be the minimum, not the objective
The latest Legionella figures provide an important reminder that water safety requires continuous attention.
In England and Wales, reported cases fell significantly in 2024.
In Scotland, reported cases increased.
Neither statistic changes the fundamental responsibility of those who manage buildings and water systems.
Legionella risk management is ultimately about people.
It is about the employee using a shower at work.
The resident turning on a tap.
The hotel guest stepping into a bathroom.
The patient in a healthcare environment.
The tenant in a residential property.
The contractor working within a building.
The visitor using a leisure facility.
Every one of these people should be able to use a building without being exposed to an avoidable risk created by poor water-system management.
For facilities managers, landlords and health & safety professionals, the strongest response to the latest figures is therefore not to ask whether the number of cases went up or down.
It is to ask:
“Would our Legionella management system stand up to serious scrutiny today?”
If the answer is yes, that confidence should come from evidence — not assumptions.
If the answer is no, the latest statistics provide a timely reason to act.
Effective Legionella management is not about having the right paperwork.
It is about having the right system, the right controls, the right competence and the right culture to keep people safe.
Sources and further guidance
The principal sources for the figures and guidance discussed in this article are:
- UK Health Security Agency — Legionellosis in residents of England and Wales: 2024. The report covers cases with symptom onset between 1 January and 31 December 2024.
- Public Health Scotland — Legionnaires’ disease in Scotland: surveillance report 2024.
- Health and Safety Executive — L8: Legionnaires’ disease: The control of legionella bacteria in water systems, the Approved Code of Practice and associated guidance for dutyholders.
- Health and Safety Executive — HSG274: Legionnaires’ disease technical guidance, which provides technical guidance for controlling Legionella risks in water systems.
- Health and Safety Executive — Legionnaires’ disease: what you must do, covering risk assessment, responsible persons and control arrangements.
This article is intended as general information and should not be treated as a substitute for a competent, site-specific Legionella risk assessment or professional health and safety advice.
