Separate Systems, Shared Outbreaks: How the UK and EU Cooperate on Infectious-Disease Surveillance After Brexit

How the UK and EU cooperate on infectious-disease surveillance after Brexit — and how to make the connection faster.

Brexit changed Britain’s relationship with European public-health institutions. It did not change the epidemiology of Europe.

A respiratory virus circulating in France can reach Britain within hours; a foodborne outbreak can involve products distributed across several European countries and the United Kingdom; antimicrobial-resistant organisms can move through hospitals, communities, animals, food and international travel; and mosquitoes, ticks and migratory wildlife pay even less attention to regulatory boundaries. The United Kingdom and European Union therefore face an unusual health-security problem: they operate separate legal and institutional systems while remaining part of the same epidemiological neighbourhood.

Understanding how they now cooperate is more complicated than saying that Britain either remains inside European disease surveillance or left it entirely, because neither description is accurate. The post-Brexit architecture is layered. Some cooperation is guaranteed by the UK–EU Trade and Cooperation Agreement; some depends on bilateral arrangements between the UK Health Security Agency and the European Centre for Disease Prevention and Control; some occurs through the World Health Organization and the International Health Regulations; and some information moves through disease-specific professional and laboratory networks, with additional cooperation activated during serious cross-border threats. The result is a system that still connects Britain with European health security, but connects it differently. That distinction matters — and, as with its animal-health companion, this is a question of governance rather than of politics.

What Britain left

Before Brexit, the United Kingdom participated in the European Union’s health-security architecture as a Member State. At the centre of European communicable-disease surveillance is the European Centre for Disease Prevention and Control (ECDC), which coordinates epidemiological surveillance across the EU and European Economic Area, conducts threat assessment, supports outbreak investigation, maintains surveillance networks and works with national public-health authorities. European infectious-disease surveillance is therefore not simply a collection of national statistics; Member States contribute to a wider surveillance environment in which data can be compared, unusual patterns identified and cross-border threats assessed.

Two further mechanisms sit alongside it. The Health Security Committee brings Member States and the European Commission together to coordinate preparedness and responses to serious cross-border threats to health, while the Early Warning and Response System (EWRS) provides a secure channel through which European authorities can communicate information about threats requiring coordination or action. EU health-security legislation was substantially strengthened after COVID-19: Regulation (EU) 2022/2371 on serious cross-border threats to health reinforced surveillance, preparedness planning, reporting, risk assessment and coordination through ECDC, EWRS and the Health Security Committee. The UK is no longer an EU Member State participating in this architecture on the same basis. That, however, is where the story begins rather than ends.

The Trade and Cooperation Agreement built a bridge

The UK–EU Trade and Cooperation Agreement, which governs much of the post-Brexit relationship, specifically recognises health security as an area requiring continued cooperation. Its health-security provisions matter because they acknowledge a basic epidemiological reality: a serious cross-border threat affecting one side may also affect the other.

The Agreement therefore allows cooperation during significant health threats. Under its arrangements, the European Union can grant the United Kingdom ad hoc access to the Early Warning and Response System where a serious cross-border threat makes such access necessary or appropriate, and can invite the United Kingdom to participate in meetings of the Health Security Committee concerning a relevant threat. This is quite different from permanent membership: Britain is not continuously sitting inside these systems as another Member State. Instead, the architecture allows the connection to become stronger when circumstances require it. In One Health Security terms, this is a form of escalated interoperability — the systems remain institutionally separate during normal operation but can become more closely connected when the biological threat crosses their boundaries.

UKHSA and ECDC built another bridge

The legal framework is only one part of the relationship. In December 2021, ECDC and the UK Health Security Agency signed a Memorandum of Understanding covering communicable-disease prevention and control, providing for information exchange, technical consultation and cooperation when emerging health threats may affect either the European Union or the United Kingdom, and envisaging exchanges of expertise and potentially personnel or liaison arrangements. That relationship became more operational in 2024, when UKHSA and ECDC agreed a Joint Action Plan implementing the memorandum; the UK Government subsequently reported that the plan had established collaborative relationships between British and ECDC specialists across a broad range of health-protection and health-security areas.

This is important because effective disease surveillance depends on much more than formal diplomatic notification. Scientists need to speak to scientists; epidemiologists need to compare interpretations; laboratories need to understand what their counterparts are finding; and surveillance specialists need to know whether an unusual domestic signal is also appearing elsewhere. Formal agreements create permission to cooperate. Professional networks make cooperation useful.

Britain still appears in European health-security discussions

The relationship is therefore not theoretical. UKHSA has continued to participate in specific Health Security Committee activity: in July 2024 it presented work on strengthened International Health Regulations and preparedness to the Committee’s General Working Group, and in January 2025 it presented its surveillance system for human metapneumovirus. These are small examples, but they illustrate something important about the post-Brexit architecture — the boundary is permeable. The UK is outside the EU institutional system, but technical interaction continues where there is mutual value. The question for preparedness is whether that permeability is sufficient during a rapidly developing biological event.

The WHO provides another layer

The UK–EU relationship also sits inside a larger international surveillance system. Both the United Kingdom and EU Member States are parties to the World Health Organization’s International Health Regulations (2005), which establish obligations relating to surveillance, assessment, notification and international response to events that may constitute public-health emergencies of international concern. Countries maintain National IHR Focal Points through which urgent public-health information can be communicated with WHO, and WHO’s Regional Office for Europe spans considerably more than the European Union.

European health security therefore operates through overlapping geographical layers — national surveillance, UK–EU cooperation, EU/EEA surveillance, WHO European surveillance and coordination, and the global International Health Regulations. Brexit altered one layer. It did not remove Britain from the others.

Surveillance is increasingly genomic

The importance of cooperation has grown because infectious-disease surveillance itself is changing. Traditional surveillance asks how many cases occurred, where they occurred and whether incidence is increasing; genomic surveillance adds another dimension, asking whether pathogens detected in different places are genetically related. That transforms cross-border investigation. A Salmonella isolate detected in Britain may be closely related to isolates appearing in several European countries; an influenza virus can be compared with viruses circulating elsewhere; and variants of emerging pathogens can be followed geographically and over time.

The more precise biological surveillance becomes, the less satisfactory purely national visibility becomes. A genome does not become epidemiologically meaningful simply because it has been sequenced — it becomes meaningful when it can be compared. This creates a post-Brexit requirement deeper than merely exchanging outbreak notifications: Britain needs continued access to the comparative biological context surrounding the pathogens it detects, and Europe needs the same from Britain. It is the same source-tracing logic that runs through our explainer on how investigators work out where Salmonella came from.

Foodborne disease demonstrates why this matters

Foodborne outbreaks provide an especially clear example. A person becomes ill in Britain, another in France, and several more in Germany and the Netherlands; initially, nothing necessarily connects them. Whole-genome sequencing may then reveal that their bacterial isolates are closely related, and the investigation shifts from four apparently national events towards one potentially international event. Food-chain information may reveal that products or ingredients moved through several countries before reaching consumers.

No national surveillance system can reconstruct that incident efficiently by looking only inward; the biological relationship creates the need for institutional cooperation. This is precisely why the distinction between institutional borders and epidemiological borders matters. The institutions stop at national boundaries. The outbreak does not. The point applies directly to the governance gap in food-safety surveillance we have examined elsewhere.

Respiratory surveillance presents the same problem at scale

Respiratory viruses make the problem even more obvious. ECDC increasingly treats respiratory-virus surveillance as an integrated system combining multiple information sources to understand acute respiratory disease and guide public-health action, while Britain operates its own sophisticated respiratory surveillance through UKHSA and health services across the four nations. Both systems may therefore be watching many of the same biological phenomena from opposite sides of an institutional boundary.

Influenza circulating in Western Europe matters to Britain, and a novel variant emerging in Britain matters to Europe; changes in severity, antiviral resistance, vaccine effectiveness or transmission patterns may become clearer when information is considered across larger populations. This produces another useful distinction: national sovereignty over surveillance does not remove the need for international context.

Antimicrobial resistance makes separation even harder

Antimicrobial resistance (AMR) creates an even more explicitly One Health problem, because resistance can emerge and move through healthcare, communities, animals, food systems and the environment. ECDC’s strengthened programme explicitly identifies antimicrobial resistance and healthcare-associated infection as major priorities and emphasises a One Health approach involving cross-sector coordination. The UK has its own substantial AMR surveillance and policy infrastructure — but resistant organisms can cross the Channel just as easily as susceptible ones.

The relevant surveillance environment therefore includes human clinical isolates, veterinary data, food surveillance, genomic information and, increasingly, environmental signals. This means UK–EU health-security cooperation cannot sensibly be confined to waiting for the next pandemic. Routine biological threats such as AMR require long-term technical interoperability.

The governance gap after Brexit

None of this means the current system is failing. It does mean that separation introduces a potential source of governance latency. Consider a rapidly emerging outbreak: a European surveillance system identifies an unusual cluster; the information is assessed; its relevance to Britain becomes apparent; UK authorities are informed; British surveillance data are examined; technical discussions occur; laboratory and epidemiological information is exchanged; and a joint understanding emerges. Each stage can work correctly. The relevant governance question is how long the entire sequence takes.

Before Brexit, some of these relationships existed within common EU institutional mechanisms; after Brexit, additional interfaces exist between the systems. Interfaces are not necessarily bad — they simply need to be designed and tested. The danger is not political separation itself. The danger is informational friction, the same theme explored in our analysis of what happens when surveillance systems connect but institutions do not.

The UK–EU reset recognises the problem

The relationship is also continuing to evolve. At the UK–EU Summit in May 2025, both sides agreed a Common Understanding covering areas in which cooperation should deepen, and health security was explicitly included. The European Commission and United Kingdom agreed to explore further exchange and cooperation on the detection of, preparedness for and response to emerging health threats, including measures intended to prevent and mitigate future pandemics and health crises, and stated that health security, biological security and chemical security should form part of regular exchanges at appropriate levels.

This suggests movement beyond an architecture designed primarily around emergency access. The long-term objective could be a relationship in which routine technical cooperation creates the trust and interoperability required when a serious incident occurs — a sensible direction, because emergency cooperation works best when the relationships do not begin during the emergency.

What should closer cooperation actually look like?

The obvious answer would be to say that Britain and Europe should simply share more information, but that is not precise enough. The objective should be interoperable surveillance. The UK does not necessarily need to replicate every component of EU surveillance, nor does every British dataset need to flow continuously into European systems; instead, both sides need to know which information becomes essential when particular biological thresholds are crossed.

That requires pre-agreed escalation arrangements. An unusual genomic cluster involving both jurisdictions might trigger enhanced exchange; a novel pathogen could trigger temporary UK participation in relevant European technical groups; a major change in antimicrobial resistance could trigger joint laboratory analysis; and an emerging vector-borne disease could require environmental, human and animal-health information to be considered together, as the spread of disease-carrying mosquitoes across Europe already demonstrates. The architecture should therefore become more permeable in proportion to the threat.

From ad hoc access to rehearsed access

The Trade and Cooperation Agreement’s provision for ad hoc UK access to EWRS is valuable, but emergency access mechanisms should be exercised. A password, protocol or legal permission that has never been used under realistic conditions is not the same thing as an operational capability. UK and EU health-security exercises should therefore test how quickly enhanced information exchange can be activated.

A simulation could begin with an unusual cluster detected in several EU countries, after which British genomic surveillance identifies related cases. The exercise would measure when UK authorities become aware of the European signal; how quickly relevant data can be exchanged; when EWRS access becomes appropriate; how quickly technical specialists are connected; whether terminology and data structures are compatible; and how long it takes to produce a shared epidemiological picture. That would convert political cooperation into measurable preparedness.

Measure cross-border governance latency

The same exercise could introduce another useful metric. Cross-border governance latency would measure the interval between information becoming relevant to both systems and that information being connected sufficiently to support coordinated action. This should not become a league table comparing Britain with the EU; its purpose would be to identify friction.

Perhaps legal permissions create no meaningful delay but incompatible data formats do; perhaps laboratory information moves quickly while epidemiological information does not; perhaps technical teams cooperate effectively but formal escalation happens too slowly. Those are solvable problems — but they have to be visible before they can be solved.

Build a UK–EU health-security bridge, not another bureaucracy

The answer does not need to be another large institution. UKHSA and ECDC already exist; the Health Security Committee already exists; EWRS already exists; WHO already provides an international layer; and national surveillance systems already generate enormous amounts of information. The priority should be strengthening the bridges.

A more mature UK–EU health-security architecture could include regular senior and technical dialogue, standing relationships between surveillance specialists, laboratory interoperability, predefined genomic data-sharing procedures, routine joint horizon scanning, reciprocal participation in selected exercises, and clear escalation criteria for serious cross-border threats. One particularly useful development would be a permanent UK–EU Health Security Liaison Mechanism — not necessarily a large organisation, but one whose purpose would be to maintain the operational connections between systems so that they do not have to be rebuilt during every incident.

One Health needs to be included

The cooperation also needs to extend beyond conventional human infectious-disease surveillance, because the biological threats we are increasingly concerned about do not remain inside the health service. Avian influenza involves wild birds, poultry, mammals and occupational exposure; AMR connects healthcare, livestock, food and the environment; vector-borne diseases depend on mosquitoes, ticks, wildlife, climate and human movement; foodborne disease connects animals, agriculture, commercial supply networks and patients; and wastewater can produce signals before conventional clinical surveillance sees them.

A mature post-Brexit surveillance relationship should therefore connect not simply UKHSA to ECDC, but the wider networks surrounding them. On the UK side, that can include animal-health, food-safety and environmental bodies; at European level, it can involve ECDC alongside organisations such as EFSA and relevant European Commission systems. The objective is not institutional tidiness. It is ensuring that the information follows the biology.

Separate systems can still create shared visibility

There is nothing inherently wrong with Britain and the European Union operating separate public-health systems; the problem would arise only if institutional separation created epidemiological blindness. So far, the post-Brexit architecture has avoided a complete break: the Trade and Cooperation Agreement provides formal health-security mechanisms, UKHSA and ECDC maintain direct cooperation, technical engagement with the Health Security Committee continues, and WHO provides another international surveillance layer. The UK–EU reset is now creating an opportunity to deepen those arrangements further.

The next stage should therefore concentrate less on whether Britain is formally inside or outside particular institutions and more on whether the combined system produces the outcome that matters. Can an unusual biological signal detected in Stockholm, London, Paris or Brussels become shared intelligence quickly enough for everybody who needs it? Can genomic evidence cross the institutional boundary as rapidly as the pathogen crosses the geographical one? Can human, animal and environmental signals be connected before an outbreak becomes a crisis? Those are better measures of health-security cooperation than institutional membership alone. Brexit changed Europe’s public-health architecture. It did not divide its epidemiology. The task now is to ensure that two separate systems can still see the same outbreak.

The post-Brexit architecture at a glance

United Kingdom

• UK Health Security Agency — national infectious-disease surveillance, laboratory science, genomic surveillance, threat assessment and incident response.
• Department of Health and Social Care — policy, ministerial responsibility and UK health-security governance.
• Devolved public-health systems — Public Health Scotland, Public Health Wales and the Public Health Agency in Northern Ireland operate surveillance and response functions within their respective nations.

European Union

• European Centre for Disease Prevention and Control (ECDC) — EU/EEA communicable-disease surveillance, threat detection, risk assessment and technical coordination.
• Health Security Committee — Member State and Commission coordination for serious cross-border health threats.
• Early Warning and Response System (EWRS) — secure rapid communication concerning serious cross-border health threats.
• European Commission — legal and policy coordination under EU health-security legislation.

Connecting architecture

• UK–EU Trade and Cooperation Agreement — formal framework allowing health-security cooperation, including potential ad hoc UK access to EWRS and participation in relevant Health Security Committee discussions.
• UKHSA–ECDC Memorandum of Understanding — direct technical cooperation and information exchange.
• UKHSA–ECDC Joint Action Plan — operational implementation of that relationship since 2024.
• WHO International Health Regulations — wider European and global notification and coordination framework.
• 2025 UK–EU Common Understanding — commitment to explore deeper cooperation on detection, preparedness and response to emerging health threats.

Related One Health Security analysis

This is the public-health companion to Outside the System, Inside the Risk (animal-disease pressure and the UK after Brexit) and Five Outbreaks, One Veterinary System (planning for simultaneous crises). It also connects to When Surveillance Systems Connect but Institutions Do Not and our explainer on what One Health Security means.

Questions & Answers

References and further reading

1. European Union and United Kingdom (2020). Trade and Cooperation Agreement — in particular the provisions on thematic cooperation and serious cross-border threats to health. GOV.UK.
2. European Parliament and Council (2022). Regulation (EU) 2022/2371 on serious cross-border threats to health. EUR-Lex.
3. European Centre for Disease Prevention and Control (2021). ECDC signs Memorandum of Understanding with UK Health Security Agency. Signed 1 December 2021.
4. World Health Organization (2005). International Health Regulations (2005).
5. UK Government and European Commission (2025). UK–EU Summit: Common Understanding, 19 May 2025.
6. European Centre for Disease Prevention and Control. Surveillance, threat assessment and the Early Warning and Response System. ECDC.