With the arrival of warmer weather, the tiger mosquito (Aedes albopictus) population has significantly increased in the Basque Country. First detected in 2014, this invasive species is now established in 72 municipalities, two more than last year, and its spread is accelerating due to the warming temperatures along the Cantabrian coast. Bizkaia and Gipuzkoa are the most affected provinces, particularly in the metropolitan areas of Bilbao and San Sebastián and along the coast, where this mosquito favors urban environments.
Despite its short lifespan, its bites, besides being annoying and painful, can transmit serious diseases such as dengue, zika (harmful to fetuses), yellow fever, chikungunya, and the Mayaro virus. While no indigenous cases of these diseases have been recorded in Euskadi, the rise in international travelers increases the risk of local transmission, as seen with a chikungunya case in Hendaye last summer.
Guillermo Herrero, director of the Public Health Department, stated that the tiger mosquito is "an important public health challenge" requiring fundamental control measures. A guide has been developed in collaboration with Neiker and several municipalities (Bilbao, Erandio, San Sebastián, Vitoria, and Zarautz). The guide recommends that local administrations appoint a point person, conduct awareness campaigns, and maintain an incident registry.
Experts emphasize the importance of citizen collaboration, as 70-80% of breeding sites are found in private homes or gardens due to the small amounts of water needed for egg-laying. Therefore, residents are urged to avoid water accumulation in containers, gutters, or plant pots and to frequently change water in birdbaths or paddling pools, which would eliminate "half the problem."
The guide also suggests that more affluent municipalities should control breeding sites and maintain urban gardens, along with implementing a comprehensive vector control plan. Although complete eradication is unfeasible, reducing its presence would alleviate public nuisance and health risks. The Department of Health will conduct new surveys in smaller municipalities to estimate its spread.
Citizens are advised, in addition to preventing breeding grounds, to use repellents and mosquito nets. Residents can also assist by identifying the tiger mosquito via the Mosquito Alert mobile app. These mosquitoes are small (around 5 mm), diurnal, and can bite multiple times consecutively.
The Bilbao City Council has launched its own control plan. According to Ana Collía, the Council's Director of Health and Consumption, the city faces "a high-risk scenario but also possesses good operational capacity." The council is developing an integrated plan requiring coordination across departments such as gardening, cleaning, and sanitation. Preventive measures implemented since June include frequent water changes in ponds and ornamental fountains, removal of water-accumulating debris, and regulation of water storage in urban gardens.
Collía highlighted that municipalities can have a "significant impact" on controlling the tiger mosquito plague, but the key lies in a "coordinated and sustained preventive strategy" based on surveillance, urban maintenance, and public awareness. Given that 80% of breeding sites are on private property, "it is essential to combine local action with citizen collaboration" to prevent the emergence of new foci.
