Pandemic Preparedness: UKHSA Shares High-Risk Pathogen List

The UK Health and Security Agency (UKHSA) has released a list of 24 high-risk pathogens that could pose potential threats to public health.

The initiative aims to strengthen the UK’s pandemic preparedness efforts.

Specifically, it aims to steer R&D efforts in diagnostics, vaccines and treatments for potential pathogens of concern.

The UKHSA’s Centre for Pandemic Preparedness developed the list. It includes a range of viruses, bacteria and other infectious agents considered to pose the greatest threat to public health in the event of an outbreak.

Among those highlighted are respiratory viruses with pandemic potential, antibiotic-resistant bacterial pathogens and emerging zoonotic diseases.

High-priority pathogens on the list include Nipah virus, mpox and chikungunya.

Also on the list are COVID-19, avian or bird flu, norovirus, Ebola and group A and B strep.

The list also includes mosquito-borne illnesses that could become common as rising temperatures from climate change increase their spread.

Due to growing concerns over resistance to existing antibiotics, it also includes bacteria such as those causing gonorrhoea.

The UKHSA said there is no ranking within the list. However, each disease or pathogen has a rating of high, moderate or low pandemic and epidemic potential.

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The family of Paramyxoviridae viruses, which includes measles, is on the list as well.

Measles has re-emerged as a public health concern due to declining vaccination rates. This has resulted in outbreaks in several countries, including the UK and the US.

Health officials warn that the highly contagious virus poses serious risks, particularly to unvaccinated children and vulnerable populations.

In March 2024, the UKHSA joined forces with the Pirbright Institute to advance vaccine development against henipaviruses. The group of viruses, including Nipah, causes severe respiratory and neurological illnesses in humans through animal-to-human transmission.

The UKHSA list will complement international efforts, including the WHO’s bacterial priority pathogen list, but is tailored to reflect the UK’s specific public health landscape.

Pandemic Preparedness, Pandemic Pathogens

The WHO has also expressed the urgent need to prepare for ‘Pathogen X’ or ‘Disease X’ — a placeholder term to describe an unknown pathogen with the potential to trigger a future epidemic or pandemic.

Disease X now sits alongside Zika, COVID-19, Ebola and Marburg virus diseases as a top priority for global research, development and investment.

Though UK-focused, the UKHSA list has global implications. As the COVID-19 pandemic showed, pathogens do not adhere to borders.

UKHSA officials underscored that the list is a strategic roadmap to foster collaboration between government, academia and industry. By identifying priority threats, the agency hopes to accelerate research pipelines and encourage the development of next-generation technologies and therapies.

“We are using the tool as part of our conversations with the scientific community, to help ensure that investment is focused to where it can have the biggest impact,” said UKHSA chief scientific officer Isabel Oliver said in the announcement.

“We hope this will help to speed up vaccine and diagnostics development where it is most needed, to ensure we are fully prepared in our fight against potentially deadly pathogens.”

Dame Jenny Harries, chief executive of the UKHSA, said: “Our scientific capability and the introduction of new interventions are all helping to keep people safe and well, but our report also highlights that we have plenty of work and opportunities ahead.”

The agency said it will update the list regularly to stay aligned with evolving threats and emerging science.

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Driving Vaccine and Therapeutic Innovations

Significant progress has been made in vaccine development for several diseases on the UKHSA’s high-risk pathogen list.

In 2024, the Africa Centres for Disease Control and Prevention (Africa CDC) declared mpox a public health emergency of Continental Security. Globally, cases of mpox have been on a sharp rise. In response, Moderna is conducting a Phase I/II clinical trial in the UK for its mRNA-based mpox vaccine, mRNA-1769.

According to reporting from Global Data, chikungunya, a virus spread by mosquitos, also remains a key focus. Last month, French biotech Valneva’s single-dose chikungunya vaccine, Ixchiq, received approval from the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) for adult use.

On March 24, the company announced it would supply 40,000 doses to the French overseas territory of Réunion to help contain a growing outbreak on the island. Additionally, a $41.3 million partnership with the Coalition for Epidemic Preparedness Innovations (CEPI) is supporting broader access to Ixchiq in low- and middle-income countries.

The 2024–2025 season saw another intense wave of influenza and respiratory syncytial virus (RSV). This led to a second consecutive year of heightened activity and hospital admissions since the pandemic. Levels were comparable to those of 2022–2023.

The rollout of new RSV vaccination programs for older adults and pregnant women has already had an impact. Interim findings show a 30% reduction in RSV-related hospital admissions among 75- to 79-year-olds.

Despite the advances in vaccine development, vaccine uptake has been on the decrease.

Richard Pebody, director of Epidemic and Emerging Infections at UKHSA, said: “We have also seen vaccine uptake decrease for a number of infectious diseases, including measles, whooping cough and in certain groups eligible for the flu vaccine, such as under 65 at risk, pregnant women and health care workers.”

Monitoring Outbreaks

According to The Infectious Diseases Impacting England: 2025 report released this week, there was an increase in both endemic illnesses and vaccine-preventable infections in the country. In 2023–2024, infectious diseases accounted for over 20% of hospital bed occupancy. This cost the healthcare system nearly £6 billion.

The US CDC reported that the highest combined hospital demand from COVID-19, influenza and RSV so far this season occurred during the first week of February. However, it remained below last season’s peak.

The agency said influenza activity continues to be high across much of the country.

As of March 20, 2025, the measles outbreak in the US involves 378 confirmed cases.