For the first time, the dengue virus has been detected in local mosquito populations in the canton of Basel-Stadt, Switzerland. This marks the first documented evidence of the virus’s presence in insects north of the Alps, raising public health surveillance concerns.
The discovery was made during a pilot surveillance program that focused on mosquitoes of the Aedes genus, which includes the Asian tiger mosquito. According to a report released Tuesday by the cantonal laboratory of Basel-Stadt, this finding is unprecedented given the local climate conditions.
Limited Spread
While the virus was detected, the viral load was low, suggesting that its spread within the local mosquito population is currently extremely limited. The mosquitoes analyzed were collected from various sites in the Basel region, including parks and gardens, during the autumn of 2024.
Dengue virus has spread significantly worldwide in recent years, with a marked increase in the number of cases. Initial transmission has also been observed in Europe. However, the Swiss Federal Office of Public Health reports that no cases of local dengue transmission have been reported in Switzerland to date.
Experts emphasize that the risk of infection not related to travel remains very low at this time. Effective transmission of the dengue virus requires very high summer temperatures, unlike other viruses such as chikungunya. This finding underscores the importance of continued monitoring and research into the potential for vector-borne disease spread as climate patterns shift.
