Yes. Legionnaires’ disease is a notifiable disease in England and Wales, and the law puts the duty to notify a suspected case on the diagnosing clinician and the laboratory — not on you as the building’s duty holder. That one fact settles most of the confusion this question hides.
The trap is reading “notifiable” and assuming you, the responsible person, have a call to make the moment a case is mentioned. You usually do not. What you might have instead is a separate, differently-named report under RIDDOR — and the two get mixed up constantly. So let me put them side by side, so you can see at a glance which one, if any, is actually yours.
The real decision: two “reports” that get confused
When someone asks whether Legionnaires’ is notifiable, they are really asking three things at once: is it on the official list, who has to report it, and is that me? The answers separate cleanly once you split two legal routes that share almost nothing but the word “report”:
- Statutory notification of a notifiable disease — a public-health channel.
- A RIDDOR report of a work-related case — a health-and-safety channel.
The same patient can sometimes trigger both. But they have different reporters, recipients, legal bases and triggers — and treating them as one thing is how duty holders end up either reporting something that was never theirs or missing the single duty that genuinely is.
Statutory notification versus RIDDOR, side by side
Read this table down each column, not across the row. The left column is the public-health notification that happens for every case; the right is the work-safety report that only sometimes lands on the duty holder.
| Axis | Statutory notification (notifiable disease) | RIDDOR report (work-related case) |
|---|---|---|
| Who must report | The diagnosing clinician and the diagnostic laboratory | The employer or person in control of the premises — the duty holder |
| Who they report to | The local authority / local health protection team, feeding UKHSA surveillance | The HSE |
| What triggers it | Any suspected or confirmed case of Legionnaires’ disease (legionellosis) | A case with reasonable evidence it was caused by exposure at work |
| Legal basis | Health Protection (Notification) Regulations 2010 | RIDDOR — the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations |
| Is it the duty holder’s job? | No | Sometimes — only where there is a work link |
The asymmetry in the bottom row is the whole point. Notification happens for every diagnosed case, automatically, through clinical hands. A RIDDOR report is conditional, and it is the only one of the two that can be yours.
Statutory notification: the clinician’s duty, not yours
Legionnaires’ disease, and the wider group legionellosis, is a notifiable infection. Under the Health Protection (Notification) Regulations 2010 a registered medical practitioner who suspects a case must notify the local authority or health protection team, and diagnostic laboratories notify their confirmed identifications. Those notifications are what feed UKHSA’s national surveillance and trigger the investigation machinery when cases cluster [1].
The duty here belongs to the doctor and the lab. As a duty holder you do not “notify” a notifiable disease — there is no form for you to file under this route. In practice this channel is usually how you first hear that anything is wrong: a health protection nurse phones you because a confirmed case has named your site within the incubation window, and asks how your water systems are run. How that case is then traced back through environmental and clinical sampling is the subject of Public health tracking: how Legionella outbreaks are investigated.
RIDDOR: when the report can be the duty holder’s
RIDDOR is the channel that can land on your desk. An employer or person in control of premises must report a case of legionellosis to the HSE where there is reasonable evidence it was caused by exposure to legionella bacteria at work [2][3]. The load-bearing words are work and reasonable evidence.
The cleanest example: one of your own employees develops Legionnaires’ disease and their exposure is tied to your undertaking. Diagnosis confirmed, work link established — that is a RIDDOR report to HSE, and the duty to make it is yours, not your water-treatment contractor’s. A consultant can advise and a service provider can help assemble the records, but the employer or responsible person pushes the button [4].
A member of the public — a guest, resident or patient — is murkier. RIDDOR’s disease provisions centre on work-related exposure, so a non-employee’s case does not map automatically onto the employer duty. Whether it is reportable turns on the specific facts, and that is a judgement to take competent advice on rather than assume either way [2][4].
So which report is yours?
Work through it by the route, not by panic:
- A case is diagnosed, anywhere. Statutory notification happens — done by the clinician and lab. Not your action, though it may be how you get the call.
- The case is an employee exposed at work. A RIDDOR report to HSE is the duty holder’s, once the diagnosis and the work link are established [2].
- The case is a member of the public possibly exposed at your premises. RIDDOR is not automatic; take advice, and cooperate with the investigation regardless.
- A high water sample but nobody ill. Neither route is triggered. There is no diagnosed disease to notify, and no case to report; it is a control failure to investigate — find the cause, act, and review the risk assessment.
Whichever applies, once your premises is associated with a case you will be asked for records, access and usually samples, and that cooperation is non-negotiable. The full sequence — clinical notification, the conditional RIDDOR report, and cooperating with the investigation — is laid out in Reporting Legionnaires disease: RIDDOR, public health and incident escalation.
One related point people fold in wrongly: the regulator you might report a case to (HSE) is not necessarily the regulator that enforces day-to-day Legionella duties at your building, which can be your local authority instead. That split is set out in Who enforces Legionella law in the UK? HSE vs local authority.
A note for the rest of the UK
The principle holds across the United Kingdom — Legionnaires’ disease is notifiable everywhere — but the legislation behind the notification, and the public-health body that receives it, differ in Scotland and Northern Ireland from the England-and-Wales position described here. If your site is outside England and Wales, confirm the local notification route and the body that runs investigations; the devolved picture is summarised in Legionella regulations in Scotland, Wales and Northern Ireland: what differs.
What this page can and cannot settle
This explains how the two reports differ and who owns each; it cannot decide your specific case. Whether a particular illness is RIDDOR-reportable, and how quickly, depends on facts you may not have on day one — the confirmed diagnosis, the work link, the exposure window — and those are judgements for a competent person working with HSE and your health protection team. None of this is legal or medical advice, and it does not replace a site-specific risk assessment. When a call comes, write down who told you what, and check the current RIDDOR criteria directly rather than relying on memory or on this page.
FAQ
A tenant or guest has been diagnosed. Do I have to notify it myself?
No. The clinician who diagnoses the case handles the statutory notification to public health; that duty is never yours. Your only potential report is a RIDDOR one to HSE, and only if there is reasonable evidence the exposure was work-related — which is not automatic for a member of the public. Either way, you must cooperate fully if the investigation links you, and keep your records and any samples intact.
Is a positive Legionella water sample a notifiable result?
No. Notification and RIDDOR disease reporting are both about a diagnosed human case, not a laboratory water result. A high count with nobody ill is a control failure to investigate — trace the cause, act on it, and review your risk assessment — not something you notify or, on its own, report as a disease. Take advice if the circumstances raise a separate dangerous-occurrence question.
Is Legionnaires’ disease notifiable across the whole UK?
Yes, it is notifiable throughout the UK, but the specific legislation and the public-health body that receives the notification are not identical in Scotland and Northern Ireland. The England-and-Wales route runs through the Health Protection (Notification) Regulations 2010 to UKHSA-linked teams; confirm the equivalent for your nation if you are outside England and Wales.
Do this now
Add one line to your water-safety file: “If a Legionnaires’ case is linked to this site, the clinician notifies public health — our only possible report is a RIDDOR report to HSE, and only where there is a work link.” Pin beside it the name and out-of-hours number of your responsible person and where the live risk assessment, monitoring records and sampling history are kept. The day a health protection nurse calls is the wrong day to be working out which report, if any, was ever yours.
Sources
[1] UKHSA, “Investigation of Legionnaires’ disease: cases, clusters and outbreaks”. https://www.gov.uk/government/publications/investigation-of-legionnaires-disease-cases-clusters-and-outbreaks [2] HSE, “RIDDOR - Reporting of Injuries, Diseases and Dangerous Occurrences Regulations”. https://www.hse.gov.uk/riddor/ [3] HSE, “Other duties: RIDDOR and notification of cooling towers or evaporative condensers”. https://www.hse.gov.uk/legionnaires/what-you-must-do/duties.htm [4] HSE, “Legionnaires’ disease - what you must do”. https://www.hse.gov.uk/legionnaires/what-you-must-do/index.htm