Résumé
Vector-borne diseases represent one of the world’s major public health challenges. Among these pathogens, arthropod-borne viruses (arboviruses) have become the most important cause of (re)emerging epidemic diseases worldwide. For many arboviruses, there are major unknowns regarding their transmission route and maintenance in nature. This knowledge gap is exemplified by phleboviruses, such as the Toscana virus (TOSV), which are mainly transmitted by sand flies and can cause meningitis or encephalitis. Despite decades of research, no reservoir host has been identified for TOSV, and based on the idea that the main transmission route must involve sand fly blood feeding, few alternative pathways have been explored. By investigating sand fly - Phlebovirus interactions experimentally, we have shown that infected sand flies spit TOSV into sugar while feeding. Furthermore, our study reveals that TOSV remains persistent and infectious for seven days in the sand fly sugar meal. Because most arbovirus vectors require a daily sugar meal, these results highlight a potentially novel horizontal transmission route operating through sand fly sugar feeding. These findings prompt further exploration of Phlebovirus transmission dynamics and emphasise the importance of environmental factors in their eco-epidemiology, particularly the hitherto unexplored role of plants.