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British Woman Gets Dengue in the South of France

A British woman contracted dengue in the South of France with researchers suggesting climate change may be to blame.

Cases of dengue, a mosquito-borne arboviral infection typically spread by the Aedes mosquito, in the UK most commonly occur in travellers who have visited Asia, South America, or Africa. In fact, the researchers behind a new case study, "Dengue in the South of France: An Emerging Health Threat?", presented as a poster at the European Congress of Clinical Microbiology & Infectious Diseases (ECCMID 2023, Copenhagen, 15-18 April), commented: "Historically, Aedes aegypti and A albopictus mosquito vectors were only found in the tropics. However, with climate change, A albopictus has now been identified throughout southern Europe, meaning that this potentially deadly virus may be autochthonously transmitted there."

In its report, Travel-associated infections in England, Wales and Northern Ireland: 2020 and 2021, the UK Health Security Agency (UKHSA) reported that, where travel history was known, the majority of dengue cases in 2020 involved travel to South-Eastern Asia and the Caribbean. In 2021, the majority of cases reported travel to Southern Asia. "The most frequently reported country of travel was Jamaica in 2020 and India in 2021," the UKHSA said. 

According to the NHS, dengue has been found in European countries, including Croatia, Italy, Spain, Portugal and Madeira, and France.

However, despite UK authorities having detected A albopictus (the Asian tiger mosquito) at UK ports multiple times over the past few years, the authors commented that "no local populations have established in the UK to date", with the NHS stating that "dengue is not found in the UK".

Rapidly Changing Epidemiology of Dengue

While an estimated 75% of cases of dengue are asymptomatic, and can go undetected, a small proportion (1-5%) of patients develop potentially fatal severe dengue or dengue haemorrhagic fever. 

The authors described the case of a 44-year-old woman who presented to a UK emergency department following a 3-day history of fevers, headache behind the eyes, muscle pain, and a blanching, widespread erythematous rash, and who had no underlying medical conditions. The woman had been visiting family near Nice in September 2022, and had returned from the South of France the day before symptoms started. Of note was that whilst staying in France, all members of the family she was staying with had been "unwell with the same symptoms".

An urgent sample was sent to the UK's Rare Imported Pathogens Laboratory (RIPL) and confirmed as acute dengue virus infection. The patient did not need any medical treatment and was monitored as an outpatient.

Dr Owain Donnelly, the Hospital for Tropical Diseases, London, and lead author, explained that the woman was part of an outbreak of over 30 locally transmitted cases in the south of France in 2022, which highlighted the "rapidly changing epidemiology of dengue".

The concern is that increasing parts of Europe and the UK will be left vulnerable to 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," Dr Donnelly cautioned.

Keep Dengue in Mind

Between June and September 2022, the Agence Regionale de Santé (ARS) in France reported three separate outbreaks of indigenous dengue virus transmission, the authors pointed out.

"Surveillance and reporting mechanisms are important in ensuring we have an accurate understanding of dengue spread," emphasised Dr Donnelly.

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, he advised, to ensure accurate diagnosis.

"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," he said.

The content of the abstract, presented as a poster at the annual meeting, had been peer reviewed by the congress selection committee, but had not yet been submitted to a medical journal for publication. The authors declared no conflicts of interest.