The beginning of the 2025 summer season has been marked by an alarming surge in imported arboviral diseases within the Toulouse metropolitan area. Numerous cases of dengue (which is actively circulating overseas), as well as — more exceptionally — chikungunya (due to an unprecedented epidemic in Réunion , which has recorded fatalities) have emerged since early May in Haute-Garonne. What is the scale of this phenomenon? Which areas are the most affected? Here’s what the latest numbers reveal as of Thursday, June 5, 2025.
Haute-Garonne: 39 Cases of Tropical Diseases in One Month, Compared to 4 Last Year
According to official data from health authorities released on June 5, 2025, the onset of this season has been explosive in the department. In one month , from May 1 to June 3, 2025, there have been 39 cases of tropical diseases reported in Haute-Garonne (18 cases of dengue and 21 of chikungunya), making it the most affected department in the region, with nearly half of all cases in Occitanie.
So far, these are only imported cases , originating from individuals who traveled abroad, mainly to overseas territories, where they were infected.
To prevent any local transmission (where individuals fall ill without having traveled to an infected area), 44 entomological surveys have been conducted by Altopictus. According to Public Health France, 10 anti-vector control treatments have been carried out in one month “in the vicinity of the cases.”
These impressive figures are even more striking when considering that in May 2024 , only four cases of dengue (and zero cases of chikungunya) were documented…
“We’ve Never Had This Much Work” in Mosquito Control
“This is a record-breaking May,” confirms Renaud Chevalier , the technical manager at Altopictus in Haute-Garonne. “We’ve never had so much work at the start of the season…”. Among the 90 entomological investigations performed by his company across the 13 departments of Occitanie, he indicates that around 40 were conducted in Haute-Garonne.
His company, which has its departmental office based in Muret, is indeed responsible for all anti-vector operations (including mosquito control campaigns ) mandated by the ARS (Regional Health Agency). They only perform these operations upon request from the ARS and after confirmed cases of tropical diseases.
How are authorities fighting these diseases?
As the ARS Occitanie reminds us, chikungunya, dengue, and Zika are diseases transmitted by the tiger mosquito, which is now present almost everywhere in France and is active between May and November. During this period, mosquito control interventions are executed around places frequented by infected individuals to limit the risk of local transmission . These interventions aim to eliminate mosquitoes before they can infect others.
Many Sick, but Few Treatments
Another surprising fact about this start of the season: among this forty field investigations, only about a dozen resulted in mosquito treatments , which equates to less than one case out of four… How can we explain these low proportions?
Many of our field investigations turned out negative. This means we did not find any tiger mosquitoes and therefore did not conduct treatment. This is explained by the particularly inclement weather conditions this month (rain and wind) in the department.
Four Treatments Wednesday Night in Toulouse
However, despite the tiger mosquitoes hiding from the weather, they have been biting more aggressively in recent weeks… and the epidemics continue to escalate. While chikungunya cases are declining in Réunion with the onset of the austral winter, dengue cases are expected to rise soon in Martinique and Guadeloupe…
On the evening of Wednesday, June 4, the teams from Altopictus conducted four treatments in the municipality of Toulouse , particularly in the neighborhoods of Lardenne, Purpan, and Borderouge.
Which Areas are the Most Affected?
In Haute-Garonne, most of the investigations conducted since early May — and the subsequent treatments — have focused on the city of Toulouse and its immediate periphery , “where the bulk of the population resides,” observes Renaud Chevalier.
“Campaigns have also taken place in northern Toulouse, especially at Bouloc , and even Plaisance-du-Touch . Conversely, since the beginning of the season in May, none have been conducted by Altopictus in Comminges.
69 Cases of Tropical Diseases over the Entire Year of 2024
For comparison, throughout 2024 , only 68 imported cases of dengue were documented in Haute-Garonne, alongside one case of chikungunya and none of Zika. Last year, however, no local cases were recorded in Haute-Garonne, unlike Hérault (three cases) and Pyrénées-Orientales (two cases).
It’s important to highlight that the majority of these figures are typically recorded during the peak and end of the summer season , between July and October, coinciding with… the return from summer vacations. Should we expect a worse situation this year?