What is dengue fever? Symptoms explained - is there a vaccine, will UK become ‘breeding ground’ for disease

Dengue fever – a mosquito-borne disease normally associated with the world's tropics – is becoming more prevalent in parts of Europe due to climate change, researchers have warned.

The caution comes after a woman from the UK was infected while on holiday in the south of France in September 2022. The 44-year-old, who has not been identified, was infected with the tropical disease during a trip to Nice. She had experienced fever, headache, muscle pain and a rash for three days but did not require further medical treatment.

Her diagnosis was made by the UK’s Rare Imported Pathogens Laboratory (RIPL) after the woman visited an emergency department after returning home to UK and doctors sent an urgent sample for analysis.

The case was presented by UK doctors to the European Congress of Clinical Microbiology & Infectious Diseases in Copenhagen. Researchers are now warning it could soon become more of an issue across Europe, with France reporting three separate outbreaks of dengue virus transmission without patients having travelled abroad, between June and September 2022 alone.

But what exactly is dengue fever, and how can you prevent yourself from getting it?

What is dengue fever?

Dengue fever "is a virus found in many parts of the world and is usually not serious", said Dr Babak Ashrafi at Asda Online Doctor.

Ashrafi said it was "a very common condition associated with travelling".

According to the NHS, it is most common in tropical areas including parts of Africa and Asia, Central and South America, the Caribbean, the Pacific islands and some southern areas of North America. You can also catch it in some parts of southern Europe during certain times of the year.

"Dengue fever is passed by infected mosquito bites," Dr Ashrafi explained, and you cannot contract dengue from another person.

Are the UK and Europe going to become a breeding ground for the disease?

Dr Owain Donnelly from the Hospital for Tropical Diseases in London said this latest case "was part of an outbreak of over 30 locally transmitted cases in the south of France in 2022, which highlights the rapidly changing epidemiology of dengue".

"With climate change, particularly hotter temperatures and more rainfall, and increasing global trade and tourism, we may see more parts of Europe with the right combination of factors for dengue outbreaks," he said. "Surveillance and reporting mechanisms are important in ensuring we have an accurate understanding of dengue spread."

Sky News reports the virus is spread by Aedes mosquitoes, native to the more temperate tropics. But one species, the Asian Tiger mosquito, is now widespread in southern Europe. It has also been detected by authorities at UK ports several times in recent years, but so far no local populations have become established.

However as average temperatures continue to rise, there is more of a chance the insects will be able to survive here.

What are the symptoms of dengue fever?

“Some people will experience no symptoms of dengue,” Dr Ashrafi said. An estimated 75% of cases are asymptomatic and can go undetected.

For those who do experience symptoms, these can include “fever, headache and pain behind the eyes, nausea and feeling achy. You may also notice a visible red blotchy rash.”

Symptoms will usually appear four to 10 days after being bitten.

“Most cases of dengue fever are mild and will pass of their own accord,” Dr Ashrafi said. “In rare circumstances, a person with dengue may find that their symptoms get worse after a few days, so remain vigilant if you or someone you’re travelling with has been bitten, as this may require hospital treatment”.

Symptoms of severe dengue include severe stomach pain, repeatedly vomiting, breathing difficulties, passing blood, bleeding nose or gums, or exhaustion or restlessness.

The NHS recommends asking for an urgent GP appointment or calling 111 if you feel unwell after travelling to a country where dengue is found. If you develop symptoms of severe dengue, it recommends calling 999 or going to A&E immediately.

Severe dengue can be very serious if it is not treated quickly, it warned. “If you have severe dengue, you'll need to stay in hospital until you recover.”

In severe cases, 1 to 5% of patients develop potentially fatal severe dengue, or dengue haemorrhagic fever.

Is there a vaccine available, and what else can you do to protect yourself from it?

While there is a vaccine available overseas, it is only recommended for people who have already had the disease - otherwise it may put them at an increased risk of having severe dengue, if they contract it later.

The NHS says there is no vaccine currently available in the UK that you can have to prevent dengue before travelling to a country where there's a risk of infection.

It advises people at increased risk of dengue - including very young people, over 65s, pregnant people, or those with weakened immune systems -  to avoid travelling to countries where the infection is found.

The mosquitoes that carry dengue bite during the day, so the best way to protect yourself is to avoid being bitten by mosquitos in the daytime if you are visiting countries with cases of the virus, the NHS says. 

Some tips that can help:

• Wear long-sleeved clothing and trousers to cover your arms and legs, particularly during early morning and early evening

• Use insect repellent on your skin (ideally one that contains the ingredient DEET)

• Close windows and doors whenever possible, or use blinds or screens

• Sleep under a mosquito nets treated with insecticide, including naps during the day