Presence of the tiger mosquito confirmed in seven municipalities since May

Since the start of the mosquito season in May, tiger mosquitoes have been detected in seven municipalities thanks to reports from citizens and field inspections. In three of these municipalities, it has been confirmed that the species survived the previous winter. Monitoring will continue until the end of October, as the tiger mosquito remains active until then. Sciensano and the Institute of Tropical Medicine (ITM) therefore encourage citizens to stay alert and keep reporting sightings.

The crucial role of citizens during the season

For the fourth consecutive year, reports from citizens through the MosquitoSurveillance citizen science platform have enabled the detection of tiger mosquitoes. Since early May 2025, citizens have observed tiger mosquitoes in six municipalities: four in Flanders (Hoegaarden, Kessel-Lo, Merelbeke-Melle and Wijnegem), one in Wallonia (Ath) and one in Brussels (Etterbeek). This marks the first observation of tiger mosquitoes in Etterbeek, while in the other municipalities they had been detected in previous years.

“We are very grateful to citizens who report sightings of tiger mosquitoes. These reports are essential for monitoring the presence and spread of the species in Belgium, which can be a vector for viruses such as dengue, chikungunya and Zika,” says Javiera Rebolledo Romero, epidemiologist at Sciensano. “The tiger mosquito season is not yet over, and Sciensano and the Institute of Tropical Medicine in Antwerp continue to rely on public participation to support surveillance efforts.

“In addition, we know that tiger mosquitoes can travel with passenger and freight traffic, hitching rides from holiday destinations in southern Europe to Belgium. We therefore encourage citizens returning by car to remain alert and take precautions to avoid unintentionally bringing these exotic mosquitoes back with them.”

Presence and overwintering

In addition to citizen reports, monitoring to confirm the overwintering of tiger mosquito populations was carried out in selected locations at the start of the mosquito season. This year, overwintering has been confirmed in three municipalities: Sint-Joost-ten-Node and Wijnegem, where the tiger mosquito was first reported by citizens in 2024, and Hoegaarden, where it was observed in 2022 and 2024. In 2025, field inspections showed the presence of the mosquito early in the season, indicating overwintering in this municipality as well. Combined with the results of previous years (Wilrijk, Lebbeke, Ath, Puurs-Sint-Amands, Kessel-Lo), the total number of locations where the tiger mosquito has been confirmed as establishing in Belgium has risen to eight. Understanding overwintering behaviour is crucial for risk assessment and for adapting control strategies against this invasive species.

According to Wim Van Bortel, entomologist at ITM, these findings are not surprising:

“Tiger mosquitoes are continuously entering the country via traffic routes, and the local climate supports their ability to survive the winter. As a result, we can expect a growing number of areas where these mosquitoes will successfully overwinter and potentially spread further.”

How to report a tiger mosquito

To report this small black mosquito with white stripes, take a photo of it and upload it via https://mosquitosurveillance.be or through the mobile application (available on Android and iOS). Tips for taking a clear, useful picture can be found at https://mosquitosurveillance.be/taking-a-good-picture. 

The MEMO+ project is a collaboration between Sciensano, the Institute of Tropical Medicine (ITM), and the Barcoding Facility for Organisms and Tissues of Policy Concern (BopCo at the Royal Belgian Institute of Natural Sciences and the Royal Museum for Central Africa), responsible for the molecular identification of exotic mosquitoes. The project is funded by the federal government and the federated entities Environment and Health through the National Environmental and Health Action Plan (NEHAP).