»Corals form the structural and biological framework of some of the most diverse and productive marine ecosystems in the world. However, increasing evidences indicate that they are severely threatened by climate changes and anthropogenic stressors. Corals naturally harbour a diverse consortium of prokaryotic and eukaryotic micro-organisms, forming together with the host the coral “holobiont”. Under changing conditions, the beneficial microbial-coral balance within the holobiont can be altered, weakening the coral physiological response and triggering the outbreak of coral diseases. Corals also host abundant viral commmunities. However, the role of viruses associated with healthy and diseased corals has been largely ignored. In this talk I will present part of my studies related to coral diseases and to the potential roles of viruses within the coral holobiont.«