Tiger mosquitoes continue to spread at abnormally high levels in France
Mild autumn temperatures have enabled the insects to proliferate, amid record dengue cases
Dengue fever is spread by mosquitoes, especially tiger mosquitoes, which are becoming increasingly common in France.
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The majority of France is on red alert against tiger mosquitoes, a specialist agency has warned, as the insect continues to spread rapidly due to mild autumn weather.
Tiger mosquitoes carry and spread diseases such as dengue fever, as well as (in much smaller numbers) chikungunya and zika. Originally from southeast Asia, the mosquitoes were first spotted in France in the Mediterranean area in 2004, and have since been confirmed in all regions and 78 departments.
Read also: Tiger mosquitoes now in Normandy, last region of France to escape them
Specialist website Vigilance-Moustiques has said that the majority of France is under red alert due to the presence of the insect, even now, in late October.
Mild autumn
The spread is largely due to relatively warm weather over the autumn, with some temperatures having been above seasonal norms. This helps the mosquitoes stay active, as they prefer warm, wet conditions. They also proliferate around stagnant water.
“When it's cold, mosquitoes go into ‘diapause’, which means they hibernate or even die in some cases,” said Dr Arezki Izri, an insect expert at Avicenne hospital (Seine-Saint-Denis), to BFMTV. “At the moment, it's hot and humid and they're taking advantage.”
“Environmental factors, including weather conditions, affect both the potential presence and seasonal activity of the tiger mosquito,” said the European Union's climate change adaptation platform Climate ADAPT.
For the mosquito to enter ‘diapause’ in autumn, the temperature needs to be below 9.5°C.
In mild-but-wet temperatures, the mosquitoes can lay eggs in dry containers, which rapidly fill up with rainwater. The insect’s eggs develop rapidly once they come into contact with water, said health agency the ARS of Auvergne-Rhône-Alpes.
Record levels of dengue
The insects’ continued presence and spread is of particular concern, with cases of dengue fever at record levels in France, even among people who have not travelled to a normally at-risk area.
Since May 1, 80 people have contracted dengue fever in France, without having travelled to a country where the disease is endemic, confirmed Santé Publique France (SPF) in a new study last week.
Read also: ‘Native’ case of dengue fever in Hérault, first in France in 2024
Similarly, a report by French health and environmental safety agency ANSES (Agence nationale de sécurité sanitaire) has even said that the probability of mainland France experiencing a dengue fever epidemic within the next five years at between 6 and 7, on a scale of 0 to 9, where 9 is the most likely.
The rise in native cases also tally - unsurprisingly - with a rise in imported cases (infections among people who have travelled to a high-risk zone).
Since the beginning of the year, SPF has recorded 3,938 imported dengue cases, 22 cases of chikungunya, and five of Zika. This is 1.5 times the number reported in 2023.
Read also: Tiger mosquitoes: dengue fever cases identified in south-west France
Read also: Dengue fever cases surge in France since start of year
The majority of these cases (68%) involved travellers returning from the French overseas territories of Guadeloupe and Martinique, which have experienced major outbreaks of the diseases for more than a year.
How to prevent the spread of dengue
ANSES recommends that people take “individual action” to fight against the spread of dengue, in support of collective measures by authorities to reduce the presence of tiger mosquitoes.
It recommends the following measures and actions:
Regularly empty saucers and other containers filled with water, to prevent them becoming mosquito breeding grounds
Cover rainwater collection tanks with mosquito netting
Protect yourself from mosquito bites by wearing long, loose-fitting, light-coloured clothing and using repellents
People arriving in France from an area where dengue is common and circulating (e.g. the French overseas territories) should also take precautions to avoid virus transmission, including:
Protecting themselves from mosquito bites;
Notifying a healthcare professional immediately if you experience any symptoms that could be early signs of a viral disease (fever, flu, etc.), and letting them know you have been in an area that has a high risk of dengue.
