As Europe confronts the increasing risk of tropical illnesses carried by the Asian tiger mosquito, a significant research advancement from the UK Centre for Ecology & Hydrology (UKCEH) is allowing scientists to more accurately identify towns throughout Europe that are at elevated risk for dengue fever.
The global movement of people, trade, and climate change is now placing half of the world’s population at risk of dengue fever*. Often called the ‘bone breaker’, this disease can lead to intense muscle and joint pain, and in severe cases, may cause internal bleeding or even death.
The Asian tiger mosquito (Aedes albopictus) has led to local dengue outbreaks in places like Paris in France, as well as in Italy and Spain, by transmitting the virus from infected travelers returning from tropical locations.
Researchers believe this invasive species is likely to establish itself in the UK in the future.
Enhancing disease prediction
Previous models for predicting disease risk indicated that vast areas, including entire regions of southern Europe, faced similar risks for local dengue incidents over extended periods. This left local authorities uncertain about whether to take protective measures.
However, the innovative modelling from UKCEH segments Europe, along with eastern Asia and North America, into 10km squares and provides daily risk evaluations for each zone. This new research undertakes a thorough examination of the entire mosquito life cycle, assessing how local climate and food competition influence factors like lifespan and egg production. This results in more precise predictions about when and where local dengue cases are likely to occur.
Already, the new model has accurately indicated several towns experiencing their first dengue outbreaks this year, including La Colle-sur-Loup, Baho, and Montpellier-Pérols in southern France, as well as Vila-seca in northeastern Spain.
Dr. Dominic Brass, an epidemiological modeller at UKCEH and lead author of the study published in Nature Communications, notes, “We foresee that the regions in Europe most impacted by dengue fever will continue to be southern France and northern Italy, attributed to a favorable climate, a stable mosquito population, and a high volume of travelers returning from tropical regions where dengue is common.”
“Nonetheless, the areas of concern are shifting further northward. Our ongoing research is focused on modeling potential future outbreaks in Europe due to climate change.”
Informing preventative action
The research team, comprising members from UKCEH, the University of Glasgow, the University of Reading, and Biomathematics and Statistics Scotland, aims for their improved predictions to assist in taking preventative actions in at-risk regions for dengue outbreaks. This can involve inspecting areas where mosquitoes typically lay eggs, like stagnant water, as done during the Paris Olympics, as well as informing the public about ways to protect themselves from bites.**
Dr. Steven White, a senior author on the study from UKCEH, emphasizes, “Our innovative modeling approach demonstrates exceptional accuracy in pinpointing the seasonal patterns and risk mechanisms for dengue fever outbreaks, serving as a crucial resource for authorities developing action plans to mitigate and control the disease’s spread.”
Swift proliferation
In regions where Asian tiger mosquitoes have already taken hold—currently in 13 countries across Europe—it is critical to identify the times of year when the risk of a dengue fever outbreak is highest and how severe that risk might be.
For areas yet to be affected, it’s vital to understand the potential risks of dengue if the mosquito species were to arrive, which can occur rapidly; for instance, Paris went from detecting the tiger mosquito for the first time in 2015 to experiencing a dengue outbreak just last year.
As of now, Paris stands as the northernmost location in Europe to report a local dengue fever outbreak and also encountered a locally acquired case of chikungunya in July, after someone was bitten by an infected Asian tiger mosquito.
The researchers at UKCEH indicate that the principles applied in the dengue fever study are transferable to other diseases spread by the tiger mosquito, like chikungunya or Zika. They are in the process of creating risk maps for these diseases.
While Asian tiger mosquito eggs have been discovered in southeastern England, the species has yet to establish a population in the UK. However, the research team cautions that this situation may alter as climate change impacts the region.
*About dengue fever
Dengue is a viral disease with no specific treatment available, although symptoms can generally be managed with common medications. Most individuals may exhibit no symptoms or only mild flu-like ones, but in certain cases, the disease can result in severe pain, internal bleeding, and even death.
Since the start of 2024, over 12 million cases and more than 8,000 deaths related to dengue have been reported across 86 countries/territories, according to the ECDC. This year’s cases have already exceeded double the total for all of 2023.
Globally, the primary vector for this disease is the Yellow fever mosquito (Aedes aegypti), which carries several viruses but is now largely absent in Europe.
Why are Asian tiger mosquitoes on the rise?
Asian tiger mosquitoes are initially from the tropical forests of Southeast Asia but have expanded their range to the Americas, Africa, the Middle East, and Europe over the past 50 years due to increased global transportation and trade. Their eggs can be hidden in used tires brought in from Asia, and adult mosquitoes can be easily transported by people.
Warmer temperatures in northern hemisphere countries increase the chances of mosquito eggs surviving, thus boosting their populations as hotter conditions enhance the replication rate of viruses.
What measures are being implemented to address this species and dengue fever?
Early and effective diagnosis of cases serves as a warning system for potential local outbreaks, allowing authorities to inform the public about associated risks.
**Personal precautions to minimize bite risks include wearing long clothing, using mosquito repellents, and installing screens on windows and doors. Individuals in at-risk zones are urged to identify potential breeding locations for mosquitoes, especially stagnant water, and ensure air conditioning drains are dry, maintain closed trash bins to avoid rain accumulation, and frequently refresh the water in birdbaths.
Local government actions during dengue outbreaks involve fumigating mosquito breeding areas, open spaces, and residences of infected individuals.
In Northern Europe, efforts are concentrated on preventing the further spread of Asian tiger mosquitoes through continuous monitoring, particularly around container ports and major shipping routes.
