In a significant development for public health in Europe, the mosquito responsible for spreading dengue fever is advancing northward in France at an alarming rate. The Asian tiger mosquito, known scientifically as Aedes albopictus, is now moving nearly three times faster than it did two decades ago, increasing its pace from 6 km per year in 2006 to an expected 20 km per year by 2024.
This rapid expansion is attributed to climate change, which is expanding the mosquito’s habitat beyond its traditional tropical and subtropical zones. According to researchers, this trend could see the mosquito establish itself in northern France within a decade, potentially reaching London, which already has a climate conducive to supporting the mosquito.
The Growing Threat of Dengue Fever
Dengue fever, a viral infection that causes severe flu-like symptoms, poses a significant health risk. While most individuals recover, the disease can be fatal if it progresses to dengue hemorrhagic fever, characterized by severe bleeding and a sudden drop in blood pressure. The World Health Organization (WHO) reports a 30-fold increase in dengue incidence over the past 50 years, highlighting the growing global threat.
Traditionally seen as a disease of the tropics and sub-tropics, dengue’s spread is accelerating due to the northward march of Aedes albopictus. This mosquito species also transmits the Zika and chikungunya viruses, compounding the public health challenges posed by its expansion.
Climate Change and Mosquito Migration
The arrival of the Asian tiger mosquito in Albania in 1979 marked the beginning of its spread through Southwest Europe. Now, as the climate warms, these mosquitoes are expanding their range northward in France, laying eggs in water where their larvae develop into adult mosquitoes, provided temperatures remain sufficiently warm.
A recent study published in Global Change Biology analyzed 35 years of data on the spread of dengue and chikungunya across Europe. It identified a shift from sporadic imported cases to local outbreaks, predicting a growing risk of endemicity, where these diseases could become regular features in parts of the continent.
Scientific Insights and Future Projections
To understand the impact of climate change on the spread of Aedes albopictus, Dr. Andrea Radici and colleagues from the Université de Montpellier developed a model combining climate data with mosquito biology. This model simulated not only where the mosquito could thrive but also the potential density of its populations, which could increase the risk of dengue transmission across Europe.
While southern Europe was already suitable for Asian tiger mosquitoes, warmer conditions are now opening new territories. The study’s simulations highlight the expansion of areas suitable for the establishment of Ae. albopictus in Europe, consistent with predictions by other studies.
“Our simulations highlight the expansion of areas suitable for the establishment of Ae. albopictus in Europe, consistent with predictions by other studies. These areas, located between 40° and 52°N, are either located over large continuous regions, such as the Spanish plateau and the French Western Atlantic region, or in isolated urban centres – London, Frankfurt, Vienna, and Zagreb,” the researchers noted.
In these urban areas, the urban heat island effect, combined with high population density, could help compensate for inadequate conditions in surrounding areas. Conversely, in warm Mediterranean regions, researchers predict a localized decrease in adult mosquito densities due to excessive summer temperatures and reduced rainfall, which limit opportunities for egg-laying and larval growth.
Implications and Future Surveillance
The findings underscore the need for enhanced mosquito surveillance, particularly in areas projected to become suitable for their survival in the coming years. The researchers suggest focusing on regions such as the western French countryside and large, populated cities between Southern England and Western Germany, including London and Frankfurt.
This development represents a significant challenge for public health officials across Europe, as they must prepare for the potential establishment of dengue and other mosquito-borne diseases in new regions. As climate change continues to alter habitats, proactive measures and international collaboration will be crucial in mitigating the spread and impact of these diseases.
