A new report from officials in Canton Basel-Stadt has revealed that the invasive tiger mosquito spread rapidly in the city last summer. Around 70 percent of Basel is now home to the invasive disease-carrying species, double the area recorded in 2022.

Area of Basel affected by tiger mosquitos doubled in 2023

According to the report, the spring and summer of 2023 saw the areas of Basel affected by tiger mosquitos double in size. The local council noted that the species can be found in 3.777 green spaces in the city, meaning around 70 percent of Canton Basel-Stadt is now a breeding ground for the mosquitos.

Last year, 388 insects in Basel were identified as tiger mosquitos, while officials found 260 different batches of eggs and larvae. What's more, experts warned that the tiger mosquito is only going to spread further once it reappears in the spring and summer of 2024.

What you need to know about tiger mosquitos

The tiger mosquito is native to the forests and jungles of Southeast Asia, but has spread worldwide thanks to international trade. The species was first detected in Switzerland in 2003 in Canton Ticino, with the first reproducing population being discovered in Chiasso in 2007.

Along with being an invasive species, tiger mosquitos are known to be potential vectors for various harmful diseases and pathogens such as dengue, chikungunya and Zika virus. However, luckily, there is yet to be a documented case of a person being infected with a disease from a tiger mosquito in Switzerland.

How does the tiger mosquito spread in Switzerland?

On its website, the Swiss Tropical and Public Health Institute explained that the mosquitos spread with the help of drivers, with the bugs following motorists into their cars. This is why the spread of the tiger mosquito in Switzerland has been largely limited to areas directly served by the motorways, especially the A2 from Ticino in the south to Basel in the north. The first tiger mosquito was detected in Basel in 2015.

Experts in Canton Basel-Stadt added that climate change has its part to play in the spread of the mosquito. Officials explained that the continually hot weather in recent years has led to a dramatic expansion in the mosquito population. It also makes the mosquito more likely to spread to other Swiss cities like Zurich, Bern, Lausanne and Geneva.

Canton Basel-Stadt plans new campaign against invasive species

Officials in the canton confirmed that the mosquito trap network - created to catch mosquitos in order to record and monitor their spread - will continue to be used in 2024, and will be expanded to include districts yet to be affected by the mosquitoes, namely Bruderholz, Hirzbrunnen, Bettingen and parts of Riehen. The canton is also planning to treat green spaces with biological larvicide to stop the mosquito from breeding.