Chestnut mosaic disease (ChMD) was described several decades ago, but for a long time its aetiology has remained unknown. Recently, combining grafting indexing and high throughput sequencing (HTS) techniques, it was possible to detect the genome of a novel DNA virus named chestnut mosaic virus, a Badnavirus, in two independent ChMD accessions (French and Italian). The virus was found to be highly associated with symptomatic plants (&gt;91%). Typical symptoms are characterized by light and dark green patches on the leaves, accompanied by shoots with asymmetric blade deformation. From May to September, the severity of symptoms increases, starting with leaf curling, light mosaic, and finally with desiccation of the leaf lamina. The severity of symptoms is inversely related to the vigor of plants and the quantity of production. The virus is transmitted by grafting, and some chestnut hybrids (i.e., Maraval) are particularly sensitive, so much so that they are suggested for wood indexing during the volunteer certification program. After the recent reconstruction of the ChMV genome and the setting up of a molecular diagnostic protocol, the detection of the virus was also recorded in asymptomatic plants. Most plants infected with badnaviruses are generally symptomless, but abiotic stress (such as temperature shifts and depletion of nutrients) can break the latency of the virus, with reemergence and an increase of severity of symptoms. This situation, which can depend on the viral variants and chestnut genotypes, opens questions on the role of asymptomatic plants in the epidemiology of the virus, and the importance of selecting ChMV-free plants from which to collect propagating materials (scions, buds) for grafting in nurseries and orchards. In the context of climate change, both viral spread and virulence could increase, with the risk of severe outbreaks.< Réduire