An outbreak of dengue fever has seen 15 people infected in the south-west of France, however none of them caught the disease locally, say health authorities. Anti mosquito measures are being stepped up as a precaution.
The 15 cases of dengue are all in Haute-Garonne, near Toulouse (Occitanie).
Dengue fever is a viral infection spread from mosquitoes to people. It is more common in tropical and sub-tropical climates, according to the World Health Organisation (WHO).
The disease is spread by tiger mosquitoes, which have become endemic to France in the past two decades, and can also spread diseases such as zika and chikungunya.
Read also: Dengue fever cases surge in France since start of year
Increased anti-mosquito efforts
The Occitanie Agence régionale de santé (ARS) has said that this year has been particularly tough when it comes to fighting dengue infections linked to the mosquito, and has stepped up its anti-mosquito efforts.
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"As soon as a case is reported to us, we intervene at their home within a radius of 150 metres to prevent a mosquito from biting them, [as it would] immediately become the vector of contamination,” said a specialist from the ARS to regional newspaper La Dépêche.
“The operation involves spraying an insecticide - deltamethrin - around the infected person's home, but also around any work, family or other places they have frequented. These alerts have increased in number over the last few days at the start of the tiger mosquito season,” the specialist said.
The 15 cases in the department are in Toulouse, and the towns of Fenouillet, Villaudric, Balma, Blagnac, Muret, and Gargas, authorities said.
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No ‘native’ cases (yet?)
So far, all of the cases identified have been in people who have returned after travelling to high-risk places, including the French overseas territories Martinique and Guadeloupe.
These islands are currently experiencing a dengue fever epidemic.
None of the 15 cases are ‘native’, meaning that none were contracted on French soil. However, this does not mean it cannot happen in future.
Dengue does not spread between humans alone. It is spread by mosquitoes when they bite an infected person and then bite someone else, transmitting the virus in the blood, which is why the anti-mosquito efforts focus on the person’s home and places they have been recently.
The ARS has still described the cases as “virulent”, and said that “the number of reported cases of infection has increased tenfold since the start of the year in the department".
“This is set to be an exceptional year, and we are very dependent on tropical epidemics,” it said.
Read also: Call for action to reduce mosquito numbers in France
Dangers of insecticide
The ARS cannot simply treat everyone or everywhere, however.
"The more you treat, the more resistant the mosquito becomes,” it said. Similarly, the insecticide used is dangerous to the environment, so must be used sparingly.
Already, authorities are not allowed to use it near any organic crops or any bodies of water.
“Deltamethrin [the insecticide used] is toxic to aquatic fauna, whereas it is not very damaging to warm-blooded animals such as humans, cats or dogs," the ARS said.
In the event of any spraying scheduled to take place near you, the local Mairie should notify you in advance, and advise you to stay indoors and keep windows closed during the treatment.
Treatments usually take place at night to limit people’s exposure to the chemicals.
Read also: Latest on tiger mosquitoes in France: where, what risk and what to do
Nationwide rise
The situation in Occitanie is being reflected across much of the rest of France, too, with the number of dengue fever cases identified soaring this year 2024.
As of May, figures showed that there had been more cases reported this year than in the whole of 2023. Figures from Santé publique France showed that from January 1 to April 30, there had been 2,166 reports of imported cases of the fever.
This compares to 2,019 cases for the whole of 2023, which was itself a record year. This is more than 16 times the number of cases reported per year on average over the past five years (128 cases).
Later in the year, between May 1 and June 18, 2024, 601 cases were recorded. All of them were imported cases, said France’s public health authority (Santé Publique France) states. Two cases of chikungunya and one case of zika virus were also recorded in France during the same timeframe.
So far, no ‘native’ cases have been recorded in mainland France this year. In contrast, in 2023, a case of native dengue fever was recorded in Paris.
Tiger mosquito spread
Tiger mosquitoes - which are smaller than ‘regular’ mosquitoes, do not ‘buzz’, and tend to bite in the morning and evening rather than at night - are now present in all regions of mainland France.
Read also: Tiger mosquitoes now in Normandy, last region of France to escape them Read also: Act now to limit tiger mosquitoes at French home this summer
They were first reported in France in the south in 2004, and have managed to spread partly as a result of global warming and higher temperatures.
They are active from May to November, and proliferate around areas of stagnant water.
People are warned to get rid of stagnant water wherever possible - including in drains and plant pots - and to use insect repellent and traps to avoid the mosquitoes.
What are the symptoms of dengue fever?
Most people who get dengue fever will show no symptoms. For those who do show symptoms, the most common are similar to flu, and include a fever, headache, muscle aches, nausea and a rash.
Symptoms typically appear four to seven days after the person is bitten.
If you have recently travelled to an at-risk area, or recently been bitten by a mosquito, and you begin to get symptoms, you are advised to report it to a GP and let them know your concerns as soon as possible.
