A warming welcome? Belgium's increasing suitability for Aedes albopictus.

Aedes albopictus, commonly known as the Asian tiger mosquito, is an invasive species of significant public health concern due to its ability to transmit dengue, chikungunya, and Zika viruses. Since arriving in Europe in the late 1970s, this mosquito species has progressively expanded its range, with Belgium marking an important step in its northward spread. The increasing frequency of its introduction raises the urgent question of whether Ae. albopictus could become permanently present in the country. This study investigates the potential for the establishment of Ae. albopictus populations in Belgium using a mechanistic model and assessing the likelihood of successful establishment based on simulated introduction events. Our results indicate that the probability of establishment is highest in Flanders, particularly under scenarios of early and multiple introductions during the summer months, even though the interannual climatic variability still plays a major role in establishment success. The establishment of Ae. albopictus in Belgium would introduce new epidemiological risks, as the species could facilitate the transmission of non-native viruses during particularly warm summers. While the transmission windows may remain limited compared to Mediterranean regions, continued introductions and climate change could expand these periods, increasing the likelihood of local outbreaks.