BBC reporters recently visited Liverpool researchers to discuss their ongoing work on emerging infections after a rare, imported case of West Nile virus was diagnosed in a UK resident. The case has highlighted the growing importance of research on mosquito transmitted infections and the need to strengthen national preparedness for diseases linked to a warming climate.

West Nile Virus belongs to a family of viruses called Flaviviridae (other flaviviruses include dengue and Zika) and primarily infects birds but can be transmitted to humans via certain species of biting-mosquito. The disease was first identified in Uganda in the 1930s and, until recently, was primarily confined to warmer regions. However, a changing climate is altering the range of the mosquitos that carry the disease and it has now been detected in several European countries including France, Spain and Italy. Fragments of West Nile Virus genetic material have already been detected in UK mosquitos, though there is no current evidence to suggest the disease is readily circulating in UK birds or mosquitos.

Liverpool researchers have a long history of research into mosquito transmitted diseases. Dr Marcus Blagrove (University of Liverpool) and colleagues have been breeding mosquito species common in the UK to investigate if they are able to transmit West Nile and other viruses. Their studies confirm that under the right conditions, these mosquitoes are competent carriers meaning they could spread the virus if it enters local bird populations.

Dr Blagrove says: “The combination of a changing climate, international travel and the ability of these insects to thrive means both invasive mosquito species and the viruses they carry are edging closer to establishing in the UK. Continued surveillance and early detection will be crucial to catch incursions before they spread.”

While most infections in humans are mild, a small proportion develop neurological disease, including brain inflammation, which can lead to long-term disability or death. There is currently no licensed vaccine specifically for West Nile virus, however, researchers in Liverpool are currently working on a vaccine that could provide protection against several flaviviruses at once, including West Nile. Dr Kris Subramaniam (University of Liverpool) and colleagues have already developed a vaccine against Zika which has undergone clinical trials, and are hoping to expand this work.

Dr Subramaniam says: “I don’t think there are any more ‘tropical viruses’… the geographic barrier of these viruses no longer exists because of climate change. This makes the work we are doing here in Liverpool to develop a vaccine increasingly important if we’re to prevent future outbreaks of these diseases.”

The presence of West Nile virus in UK mosquitoes does not mean an outbreak is inevitable. However, experts stress that preparation for West Nile and other mosquito-borne viruses is essential, including strengthening mosquito surveillance, advancing vaccine research, and ensuring clinicians recognise and diagnose infections quickly. It also requires clear communication with the public about simple prevention measures, such as reducing exposure to mosquito bites during travel or warm UK summers.

Professor Tom Solomon CBE, Director of The Pandemic Institute, said: “Diseases like West Nile illustrate why pandemic and epidemic preparedness is so important. Mosquito transmitted viruses are moving north as the climate warms. The research underway here in Liverpool aims to ensure the UK has the knowledge, infrastructure and countermeasures in place before local transmission occurs.”

Professor Solomon also recently contributed to Channel 4’s Ancient Autopsy programme discussing whether Alexander the Great might have died of West Nile virus.  “He died in Babylon, where West Nile virus may well have been circulating at the time,” Professor Solomon commented, “and the fact that he had a febrile illness with paralysis and then stopped speaking before he died is consistent with West Nile virus infection, though we will never know for sure.”

You can read more on West Nile virus, including symptoms, diagnosis and spread on the UK Health Security Agency website.