Zia Farooq, Joacim Rocklöv, Jan C. Semenza
Since 2007, outbreaks of chikungunya and dengue have become increasingly frequent and large scale in Europe. The frequency and size of these episodes suggest a concerning trend. In 2025 alone, there have been an unprecedented 81 locally acquired chikungunya outbreaks, with a total of 1124 cases to date.1 Another particularly concerning event occurred in October, 2024, when Italy had the largest recorded dengue outbreak in Europe, with more than 200 confirmed autochthonous cases.2 Although this number might seem small compared to outbreaks in endemic regions such as southeast Asia or Latin America, in the European context, it represents an unprecedented scale with epidemic potential.