Scientists are warning of the growing risk of tropical illnesses spreading due to global warming. As temperatures rise, many places are becoming more hospitable to Asian tiger mosquitoes, which are known to carry and transmit dengue fever, Chikungunya but also Zika. In France, record cases of dengue fever have been reported since the start of 2024. Most of them are in people who had travelled to French overseas territories. Authorities warn this could result in people getting infected in mainland France, in a wave of so-called native cases. The Down to Earth team investigates.