Respiratory infections pose the greatest risk to UK health security over the next 5 years, according to the UK Health Security Agency (UKHSA). In its first Health Security Risk Assessment (HSRA), the agency put the likelihood of a pandemic influenza or coronavirus scenario exceeding 25% within that period.

Despite vector-borne health risks — including Zika, West Nile virus, and tick-borne encephalitis — having lower assessed likelihood and impact, they would become a greater issue over the longer term as conditions became more favourable in the UK for transmission.

Emerging infections also pose a persistent and, in some cases, increasing threat, while antimicrobial resistance (AMR) is a key driver in determining how a number of health risks could impact UK health security over the next 5 years.

Environmental hazards, such as extreme heat and extreme cold, could cause significant health and socioeconomic disruption, and combined seasonal hazards, such as influenza, RSV, and norovirus, pose challenges for healthcare capacity and health system coordination.

Worst-Case Scenarios 

The HSRA was designed to support planning for strengthening resilience against health security risks. It is the first document UKHSA has published that systematically compares and ranks the range of health security risks it oversees.

For each of the risks included in the report, a “reasonable worst-case scenario” was created. These included scenarios for a novel coronavirus pandemic, extreme heat, and declining childhood immunisation coverage — all of which have occurred in recent years. 

In one scenario, a new strain of influenza arrives in the UK and through multiple waves over the course of 2 years leads to symptomatic infections in over half of the UK population, 4% of whom require hospital care. This outbreak, much like the COVID-19 pandemic, would have substantial wider healthcare impacts as healthcare workers became ill or were diverted to the response.

In another scenario, a series of warmer-than-expected summers in continental Europe leads to the Aedes albopictus mosquito becoming established in London and south coast ports, leading to the first locally acquired cases of dengue in the UK, some requiring hospital care.

Referencing declining MMRV (measles, mumps, rubella, and chickenpox) vaccination — where coverage remains below the World Health Organization recommendation of 95% needed for population immunity — the report noted how the UK had lost its measles elimination status. In a “reasonable worst-case scenario,” MMRV uptake continued to fall, resulting in around 160,000 cases over the period of a year, and placing considerable strain on the health system.

“These scenarios are not a prediction of what is most likely to happen,” said Professor Steven Riley, UKHSA chief data officer. “They represent the worst plausible manifestation of that particular risk.” 

Enhanced Preparedness 

The report aims to help boost pandemic preparedness and noted how past respiratory pandemics — including the 1918-1920 influenza outbreak and COVID-19 — had exposed weaknesses in public health and healthcare system resilience, capacity, and preparedness. These pandemics had also revealed how population-level vulnerabilities and health inequalities could amplify impacts.

However, the report explicitly assessed threats only. It did not assess preparedness or provide guidance on managing risk because doing so, the report said, requires different expert advice and must consider ethical, social, economic, and political factors.

The UK continues to experience risks from a set of diverse and complex health security threats, whose timing and magnitude are difficult to predict, Riley said. 

COVID-19 was a reminder of the importance of preparedness and resilience during a health crisis. Recent domestic incidents, including mpox clade Ib, botulism, meningococcal B, and hantavirus outbreaks, showed how rapidly health concerns could escalate and underscored the importance of effective strategic planning to safeguard the public’s health, Riley said.

Rob Hicks is a retired National Health Service doctor. A well-known TV and radio broadcaster, he has written several books and has regularly contributed to national newspapers, magazines, and online publications. He is based in the United Kingdom.