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How serious is the threat from dengue fever in France?

Genevieve Mansfield
Genevieve Mansfield - [email protected]
How serious is the threat from dengue fever in France?
An Asian tiger mosquito in 2021 (Photo by Manjunath Kiran / AFP)

As tiger mosquitoes are now present in over 80 percent of mainland France, health authorities are worried that local transmission of tropical diseases, like dengue fever, will increase.

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As of January 2024, tiger mosquitoes - known for their ability to carry diseases such as dengue, chikungunya and Zika virus - had been detected in 78 of France's 96 mainland départements, including the Paris region.

This has left public health authorities concerned about the spread of dengue fever in France, particularly this summer as large crowds are expected amid the Olympic Games.

READ MORE: MAP: Tiger mosquitoes reach northern France

How common is dengue fever in France?

In the first four months of 2024, 1,679 cases of dengue fever were identified in mainland France, a number that is 13 times higher than the same period last year, Le Parisien reported.

Crucially, however, none of these are believed to have been contracted in mainland France - they were all reported among patients who had recently travelled from the tropical regions where dengue fever is common.

The majority of cases were from people who had visited the Caribbean islands of Martinique and Guadeloupe - where the disease is endemic.

These islands are for administrative purposes part of France - so often show up in French health data - but they are roughly 7,000km away from Paris.

So far, there have not been any indigenous cases (autochtone - or people infected on mainland French soil) yet this year.

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Local transmission of the disease remains relatively rare. In 2023, nine separate outbreaks of indigenous dengue transmission were identified, one of which occurred in the Paris region. These led to 45 cases of local transmission (in mainland France).

Most were in southern France - in the Provence-Alpes-Côte d'Azur, Occitanie and Auvergne-Rhône-Alpes regions - though one outbreak occurred in the Paris region, according to French public health authorities.

This is less than 2022, which was a notable year with 66 total cases of indigenous dengue fever were recorded. In comparison, between 2010 and 2021, only 48 cases (total) were recorded.

What to expect for 2024

Experts believe that the number of cases in France, including indigenous ones, will grow this year, as tiger mosquitoes now occupy more territory in mainland France.

On top of that, the number of cases has increased significantly in Martinique and Guadeloupe.

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"What we see in France is a mirror image of what is happening in the French Caribbean, and more widely in Latin America and the rest of the Caribbean, where dengue fever has been circulating since the start of the year at unprecedented levels", the head of Santé Publique France, Dr Caroline Semaille, said during a press conference.

The Olympic Games will also bring an influx of tourists from all over the world, and weather conditions are expected to be conducive to mosquitoes - a year with a lot of rainfall, and potentially high temperatures. 

What is dengue fever?

The disease is spread to people from bites by infected mosquitoes.

The most common symptoms are high fever, chills, abdominal, joint and muscle pains, and vomiting. It can also cause a skin rash that resembles measles, according to France's Institut Pasteur.

Symptoms usually begin three to 14 days (with an average of four to seven) after being bitten.

However people are asymptomatic in 50 to 90 percent of cases (depending on the epidemic), which can make monitoring difficult.

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At-risk groups include the immunocompromised, children and the elderly, who are more likely to suffer from severe forms of the disease.

Deaths from the disease are very rare, occurring in around 0.01 percent of all cases, almost all in countries that have poor healthcare systems.

How can I avoid tiger mosquitoes?

Female tiger mosquitoes lay their eggs in water, and they can lay several hundred eggs at once. Therefore try to avoid having any standing water outside your home and be aware of the items that might collect rainwater.

This includes regularly emptying vases, flower pots, as well as watering cans and pots. If you want to collect rainwater, you could cover water butts with mosquito nets or fabric to keep the mosquitoes from getting inside.

READ ALSO 5 plants that (allegedly) repel mosquitoes

You can also keep your gutters clean - this helps to keep the water flowing when it rains, and it avoids any stagnant pools from building up.

To protect yourself, try to wear long, loose and light-coloured clothing, in addition to insect repellent. You might also consider wearing a mosquito net head gear.

The main difference between tiger mosquitoes and other species would be getting a bite during the day, and the fact that tiger mosquitoes are likely to bite several times. You can tell for sure if it was a tiger mosquito by seeing the insect itself. They are also silent.

There is no immediate cause for alarm if you are bitten, in almost all cases the bites are just itchy and annoying. In very rare cases, tropical diseases can be spread by the mosquitoes - seek medical help if you develop a high fever and rash.

READ MORE: How to prevent the spread of tiger mosquitoes in France

What do tiger mosquitoes look like?

They are very small, about 5 mm, and they have a highly contrasting colour, with black and white stripes on their body and legs.

If you believe you have spotted a tiger mosquito, you can report it to public health authorities online.

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