The 7 signs of deadly, paralysing West Nile virus that’s mistaken for flu – as it’s found in UK mozzies for first time
DEADLY and paralysing West Nile virus has been spotted in UK mosquitoes for the first time.
The bug is spread through the bites of infected mozzies that are common in Africa, the Middle East and South Asia.
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Many people won't get symptoms at all but some may be struck with flu-like aches and pains, headaches and fever.
The virus can cause severe, life-threatening illness in around one in 150 people who catch it, according to the World Health Organization (WHO), which may lead to paralysis or even death.
Scientists identified fragments of the virus in the genetic material of UK mosquitoes for first the time.
While there have been other cases of West Nile virus on British soil, these have usually been a result of mozzie bites acquired in different countries, where the disease-carrying critters are abundant.
Over the last 25 years, only seven cases have been brought into the UK by travellers - and none have caught it locally.
While West Nile virus is endemic in Africa, the Middle East, West and Central Asia, the US and Australia, mosquitoes carrying the disease have gradually spread through Europe - including in the north, where temperatures are lower.
The infected mozzies were found on the banks of the River Idle, near Gamston in Nottinghamshire, where flooding and standing water encourages them to gather.
Scientists from the UK Health Security Agency (UKHSA) gathered them in July 2023 and pooled into 200 groups of 10 for testing.
Only two out of 200 groups that were tested showed traces of the virus.
UKHSA stressed that it the risk to Brits was low, as there have been no reports of the virus spreading to people.
Dr Meera Chand, UKHSA deputy director for travel health and emerging infections, said: "While this is the first detection of West Nile Virus in mosquitoes in the UK so far, it is not unexpected as the virus is already widespread in Europe.
"The risk to the general public is currently assessed as very low.
"Vector research of this kind is designed to give us early warning of potential threats so that we can enhance our disease surveillance and control activities and ensure patients receive appropriate testing."
The health watchdog said healthcare professionals should test patients with encephalitis of unknown cause as a precaution through UKHSA’s Rare and Imported Pathogens Laboratory.
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Prof Tom Solomon, from the NIHR Health Protection Research Unit on Emerging Infections and the Pandemic Institute in Liverpool said West Nile virus mostly causes a flu-like illness in people.
But it can also "infect people with no symptoms at all".
People infected with the bug may experience:
- Headaches
- Body aches and joint pain
- Vomiting
- Diarrhoea
- Rash
- Fever
- Swollen lymph nodes
Symptoms typically take two to 14 days to appear after infection and should go away within three to six days, according to the UK Health Security Agency.
Prof Solomon added: "In a small proportion of patients, the virus can cause neurological disease, which may lead to paralysis or even death.
"Unfortunately, there is no specific treatment."
Vector-borne diseases - illnesses transmitted to humans by organisms such as mosquitoes and ticks - are a growing threat to the UK and Europe.
They account for more than 17 per cent of all infectious diseases globally, causing over 700,000 deaths annually, according to UKHSA.
They include:
- Malaria
- Dengue
- Yellow fever
- Zika
- Chikungunya
The Fit for Travel website says if you are travelling to an area affected by diseases such as malaria, dengue fever and yellow fever, spread by mosquitoes, you should take action to protect yourself.
Some mosquitoes are more active in the day time while others at night - so it is important to protect yourself at all times.
It says: "If you develop a high temperature (fever) either during or after travelling to an affected area, you should seek medical advice as soon as possible and give details of your recent travel history."
To protect yourself:
Use a good quality insect repellent
The higher the strength, the longer the repellent should prevent mosquitoes landing on you.
An effective repellent contains at least one of; DEET (50% concentration for areas where there is malaria), Icaradin/Picardin (at least 20% concentration, Eucalyptus citriodora oil, hydrated, cyclized (at least 30% concentration), IR3535 (but not for malaria areas).
Apply:
- On all areas of skin not covered by clothes
- After sun screen
- Regularly, particularly if you notice mosquitoes around you
- After swimming, washing or excessive sweating
- On the face, by spraying the repellent on the hands first
Loose clothing
Mosquitoes can bite through tight clothing, so loose-fitted clothing is ideal.
Consider a high neckline, long sleeves, long trousers and socks.
Remember to apply insect repellent on areas not clothed.
Mosquito nets
Mosquito nets can protect you at night when sleeping and are even better if treated with insecticide.
Check for any holes in the net before using it. If a hole is apparent, then this should be mended.
You should tuck the net under your mattress or ground sheet during the night, and either collapse it down, or keep it tucked up during the day to stop insects flying under and into the net.
Fewer than 1 per cent of people infected with West Nile virus will develop disease in the brain and nervous system, according to UKHSA.
This may be meningitis, encephalitis with high fever, neck stiffness, disorientation or confusion, severe muscle weakness, tremors, convulsions, paralysis and coma.
People over 50 or with health conditions like cancer, diabetes, kidney disease, or high blood pressure are at higher risk of serious illness.
Meanwhile, patients aged over 70 are at highest risk of death.
The bug is primarily spread through the bites of infected mosquitoes.
According to UKHSA, humans are considered dead-end-hosts, which means people infected with West Nile virus can't transmit the virus back to mosquitoes.
This means that if someone gets overseas and travels back to the UK, this won't lead to further transmission of the illness.
With the bug being spotted in UK mosquitoes for the first time, experts still aren't especially worried that this will lead to widespread transmission of West Nile virus in the UK.
Dr Robert Jones, assistant professor at the London School of Hygiene and Tropical Medicine, said: “There is currently no evidence that these fragments of genetic material are linked to any human cases of West Nile virus infection."
Professor Paul Long, a microbiologist at King’s College London, added: “Although virus-infected mosquitoes have been found in the UK there’s no evidence yet that these mosquitoes will survive in the UK climate, although prolonged warm weather does increase the chances.”
In Europe - where cases of West Nile virus have been identified in countries including France, Italy and Portugal - cases tend to be highest in summer and early autumn, when mosquitoes are most active.
In very rare cases, the illness can passed on through blood transfusion, organ donation or vertical transmission from mother to child during pregnancy, delivery or breastfeeding.
In 2024, 1,436 locally acquired cases were reported across 19 EU countries — including France, Spain and Italy - resulting in 125 deaths.
That’s a sharp rise from 802 cases in the same period last year, suggesting the virus is gaining ground.
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