Experts have warned dengue fever could be becoming more common in Europe due to climate change after a British woman was infected by the deadly mosquito-borne tropical disease while visiting the south of France. Cases of dengue seen in the UK are typically found in people who have contracted the virus while travelling in Africa, Asia or South America — but climate change appears to be increasing the range of the carrier mosquitos.
Although an estimated 75 percent of cases are asymptomatic — and often go undetected — around 1–5 percent of cases develop severe dengue, or dengue haemorrhagic fever, which can be fatal.
Dengue virus is only spread via mosquito bite, and cannot be transmitted person to person.
The 44-year-old woman presented herself at an Emergency Department in the UK four days after returning home from visiting family in Nice in September last year, who exhibited the same illness.
Her symptoms — which included fevers, a headache behind the eyes, muscle pain, and a widespread rash that disappeared under pressure — appeared one day after her return.
She had no underlying medical conditions and had not travelled to any other countries, let alone those where dengue fever is traditionally known.
A sample was collected from the patient and analysed at the Rare Imported Pathogens Laboratory in Porton Down — confirming acute dengue virus infection.
The patient did not need any medical treatment, the researchers said, and was monitored as an outpatient.
The study was undertaken by health expert Dr Owain Donnelly of The Hospital for Tropical Diseases in London and his colleagues.
Dr Donnelly said: “This individual 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.
“Surveillance and reporting mechanisms are important in ensuring we have an accurate understanding of dengue spread.
“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.”
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Historically, the species of mosquitoes that transmit dengue virus — Aedes aegypti and Aedes albopictus — were only found in the tropics.
However, climate change has altered the range of the latter species, informally known as the Asian tiger mosquito, with specimens found throughout southern Europe.
Between June and September last year, the French Agence Regionale de Santé (Regional Health Agency) reported three separate outbreaks of indigenous dengue virus transmission — that is, contracted within the country by patients who had not travelled abroad.
Here in the UK, the authorities have reported the detection of the Asian tiger mosquito at ports on several occasions in the last few years.
Despite this, however, no local populations of A. albopictus have been established in the UK so far — although this has the potential to change in the future.
Dr Donnelly concluded: “To ensure accurate diagnosis, physicians should consider testing for dengue if patients live in, or have visited, countries where Aedes albopictus is found — and present with the typical constellation of symptoms — even if dengue is not widespread.
“Making the correct diagnosis not only has an impact on patients, but also allows us to increase our understanding of dengue distribution and take appropriate steps to control outbreaks.
The full findings of the case report are being presented at the European Congress of Clinical Microbiology & Infectious Diseases, which is being held from April 15–18 in Copenhagen, Denmark.
