Tiger mosquito storms France: warming opens 'corridor' for dengue in Western Europe

A paper published in Global Change Biology showed that the invasive tiger mosquito Aedes albopictus is rapidly filling its climate niche in France using real observations and mechanistic climate-ecological modeling, which means an increase in the “biting” nuisance and a greater threat of introduction/local transmission of arboviruses (dengue, chikungunya, zika) throughout Western Europe. The authors collected data on the actual advance of the species and superimposed it on a life cycle model dependent on temperatures and habitat. The result: the rate of northern advance in France has accelerated from approximately 6 km/year in 2006 to 20 km/year in 2024, and large Western European cities - London, Vienna, Strasbourg, Frankfurt - already look climatically suitable for sustainable habitat of the species in the coming years. According to the authors, the north of France could be completely “developed” within a decade, after which it would be “easier” for the mosquito to move to the British Isles.

Background of the study

The invasive “tiger” mosquito Aedes albopictus has transformed itself in two decades from a local southern European curiosity into one of the key carriers of arboviruses (dengue, chikungunya, zika) in temperate Europe. Its biology helps it “storm” cities: eggs survive the cold and endure drought, larvae develop in tiny artificial reservoirs (from saucers under flowers to storm drains), and adults are active in the warm months. Against this background, the key question is not “can it get north”, but where the climate already allows stable populations to take hold – and how quickly such a “window” of suitability opens as the weather warms. This is precisely the question answered by a new paper in Global Change Biology, updating estimates for France and Western Europe.

The problem has long ceased to be theoretical: Europe annually registers autochthonous (local) cases of dengue - that is, infections occur on the spot, when a traveler brings the virus, and then it is picked up by mosquitoes. According to WHO/Europe, in 2024, there were 304 locally acquired cases in the region - the highest figure since observation began; in 2023, autochthonous cases were noted in France, Italy and Spain, including an outbreak in the Paris region. These signals go hand in hand with the expansion of A. albopictus, which is “closing” more and more territories in the south and center of the continent.

Climate is the main driver of this dynamic. Mechanistic models that tie the mosquito life cycle to temperature and seasonality show that as average temperatures rise, the duration of the warm season and the chance of overwintering eggs increases, which means the likelihood of sustainable colonization of new cities increases. A recent assessment for France shows not only an expansion of suitable zones, but also an acceleration of northward movement: from approximately 6 km/year in the mid-2000s to 20 km/year by 2024 - figures that are important for planning sanitary measures and early warning of risks.

The context is broader than just one country: independent studies and reviews agree that the suitability for A. albopictus in Europe is already high and will continue to increase, especially in urban areas where there are many pockets of standing water. The public health challenge therefore becomes not only monitoring for imported cases and mosquito traps, but also managing the urban environment (drainage, elimination of mini-reservoirs, communication with the population) and preparing clinics for the summer-autumn risk windows - in advance, before stable populations establish themselves in new cities.

Why is this important right now?

Aedes albopictus is a carrier of at least several dozen arboviruses and is no longer an “exclusively tropical” species: in temperate latitudes, it is helped by the survival of eggs in the cold and the ability to quickly use the urban environment - any containers with water from flower saucers to rainwater inlets. New work shows that within France, the species is close to the ceiling of its “historical” climatic niche, and further expansion of the range deep into Western Europe will be largely fueled by warming, which increases the duration of the “mosquito season” and makes wintering easier. This contradicts earlier assessments and reviews: the climatic “window” for Aedes in Europe is steadily expanding, and the risks of arboviruses are shifting north.

How the model worked

The researchers combined field data on the actual distribution of the mosquito with a mechanistic model in which key stages of the life cycle and population size depend on temperature and environmental conditions. This approach allows not only to “fit” the curves to past years, but also to calculate scenarios for the near future - where and when climate suitability appears, how many weeks a year the mosquito is active, and where conditions for local transmission of viruses are created. Unlike “purely statistical” suitability maps, the mechanism takes into account the biology of the species (development of larvae, diapause of eggs) and is better transferred to new climatic conditions.

Key findings and figures

- Acceleration of invasion: the rate of advance into northern France has increased from ~6 to ~20 km/year in less than two decades. This is consistent with the observed expansion and the increase in indigenous dengue cases in Europe.
- Target cities: London, Vienna, Strasbourg, Frankfurt are already assessed as climatically suitable for stable populations of A. albopictus. Even if the species has not yet established itself, the "window" is open.
- Niche threshold in France: the current expansion is approaching the theoretical limits of the "old" climatic niche; further expansion will depend on further warming.
- Wider than a mosquito: if the trend continues, Western Europe should prepare for an increase in the "biting" nuisance, costs for larval control and greater risks of dengue/chikungunya/zika outbreaks in summer and early autumn.

What does this change for healthcare and cities?

In practice, the study moves the conversation about “mosquitoes and climate” from abstraction to action maps. The link “models → management” is useful:

• Sanitary preparation: planned strengthening of surveillance of larval foci and monitoring thresholds where the model shows an imminent “window” of suitability; updating of diagnostic protocols for dengue/chikungunya in clinics.
• Urban environment: drainage and design (slopes, grates, storm drains without stagnant pockets), regulations for yard tanks, smart water level sensors at public works sites.
• Risk communication: “dry yard” campaigns (drain saucers/buckets once a week), “protect your skin” (repellent, clothing at dawn and dusk), screen windows.
• Precision technologies: integration of Wolbachia approaches, sterile male injections (SIT) or egg-laying traps in areas where the model predicts outbreak potential.

Context and comparison with past science

The work logically follows on from earlier assessments that the climatic suitability for A. albopictus in Central/Western Europe will increase in the coming decades. As early as 2011, forecasts showed range expansion as early as 2011–2040; recent reviews confirm that temperature and precipitation are the main drivers, with urban environments providing the mosquito with a “ladder” to the north. What is new here is the update to France and neighboring countries, testing on real invasion trajectories, and directly linking the results to arbovirus risk management.

Restrictions

This is a model study, albeit one that relies on rich observations: the actual risk of transmission depends not only on weather and mosquitoes, but also on virus import (travel), human behavior, neighborhood development, and the systematicity of municipal monitoring. Estimates of the rate of invasion are sensitive to the completeness of the foci count, and the suitability of the climate does not guarantee immediate establishment of the species. Nevertheless, the consistency of the findings with independent sources makes the picture alarmingly plausible.

What to do "here and now"

• For citizens:
  • do not keep open containers of water in yards/on balconies; empty/wash saucers under flowers once a week;
  • use repellents and protective clothing during mosquito activity hours (morning, evening);
  • If you have a fever after traveling to warm regions, tell your doctor - this helps track the import of the virus.
• For schools/kindergartens/HOAs:
  • take inventory of the “water storage facilities” on the territory, establish a drainage schedule;
  • Place mesh lids on garden barrels/reservoirs;
  • Inform parents and residents about simple preventive measures.
• To municipalities:
  • Sync climate suitability maps with complaint/trap registry;
  • test pilots (Wolbachia, SIT, smart traps) in "hot" areas;
  • prepare summer protocols in case of importation/local transmission (diagnosis, notification, focal treatment).

Where will the research go next?

The authors open source the code and scripts, making it easy to transfer to neighboring regions and update as new climate data becomes available. The next step is to take into account urban microclimates, population mobility, and the cost-effectiveness of different control strategies. For public health, there is a clear need for early warnings: linking weather data, mosquito phenology, and travel flows to predict dengue risk windows months in advance.

Research source: Radici A. et al. Aedes albopictus is rapidly invading its climatic niche in France: broader implications for biting nuisance and arbovirus control in Western Europe. Global Change Biology, 2025. https://doi.org/10.1111/gcb.70414