The changing face of infectious diseases in the UK

Two thousand and twenty-five has marked a worrying shift in the UK’s infectious disease landscape. The country faces great challenges posed by resurging vaccine–preventable illnesses, cross–species viral spillovers, and infection burden promoted by climate change. Here’s what we think is most important to know: 

Measles: return of a preventable crisis 

Measles, declared cleared from the UK in 2016, has made a concerning comeback. Major outbreaks were reported in London and the Midlands in early 2024. As of May 2025, there has been a total of 320 cases recorded since January 2025. 

This reveals a troubling reality: Measles, mumps and rubella (MMR) vaccination rates have dropped below the 95% requirement for herd immunity due to pandemic disruption and vaccine misinformation and hesitancy.   

Measles is an extremely transmissible respiratory disease, yet entirely preventable. The UK Health Security Agency (UKHSA) has urged the public to keep up to date with MMR vaccination and warns that measles outbreaks could intensify if vaccine uptake does not improve. 

H5N1: UK livestock 

H5N1 is not confined to birds alone. In the UK, infections have been documented in foxes and otters, while globally, the virus has been detected in more than 20 mammalian species, often causing mortality or severe neurological symptoms. While human cases in the UK remain exceptionally rare and have been limited to poultry workers, H5N1’s demonstrated ability to cross species barriers highlights its pandemic potential.  In March last year, H5N1 was reported for the first time in dairy cattle, with the spread now observed across 17 US states. The risk for humans remains low; however, these infections show an elevated risk for the virus evolving the capacity to transmit between humans. The UK’s minister for public health and prevention, Andrew Gwynne, reassured that the UK is ready to respond to future threats and recently added the H5N1 vaccine to its national stockpile.

Killer fungi: the unseen epidemic  

Fungal pathogens are emerging quietly and dangerously. Aspergillus fumigatus, a common environmental mould, has exhibited resistance to frontline last-resort antifungal drugs. Similar trends have been reported in other pathogenic fungal genera like Candida and Cryptococcus. These multi–drug–resistant fungi are extremely dangerous to lung disease patients and individuals with a weakened immune system. Hospital–acquired fungal infections, especially in intensive care units, have also become more prevalent.  

Climate change is another factor contributing to fungal pathogen emergence. Warmer temperatures and wet conditions extend the life and spread of airborne spores. Fungal threats are no longer confined to tropical climates or immunocompromised patients. 

Flavivirus: West Nile virus detected in the UK 

In May 2025, a research programme ran by the UKHSA and the Animal and Plant Health Agency (APHA) reported that they had identified fragments of West Nile Virus genetic material in aedes vexans mosquitoes collected from wetlands on the River Idle in Nottinghamshire. 

Prof. James Logan at the London School of Hygiene & Tropical Medicine said, “This development is serious, but it is not unexpected... It does not require public alarm, but it does call for vigilance and investment in long-term preparedness.” Climate change is bringing about more favourable landscapes for vector-borne diseases in the UK, which, alongside increased movement of people and goods, means our surveillance needs to be stronger than ever.

The convergence of vaccine hesitancy, climate change, and emerging pathogens is reshaping the UK’s infectious disease landscape in real time. 

These interconnected threats demand immediate, coordinated action, not just reactive crisis management. The Departments of Infectious Diseases and Epidemiology at Imperial are actively responding with real-time surveillance, wastewater monitoring, and predictive modelling vital to informing WHO and government policy.