Figure 1.

The expression ‘sword of Damocles’ denotes the sense of foreboding engendered by a precarious situation, whereby the onset of tragedy is restrained only by a delicate trigger. (a) A pictorial representation of the legend that generated the colloquial expression, by Wenceslaus Hollar (1607–1677), where the sword hanging above Damocles neck is depicted; (b) Honey bees are permanently threatened by covert DWV infections (1) that are normally kept under control by the bee’s immune system (2); the Varroa mite, which also causes direct damage to bees (3), can trigger viral replication and take advantage (4) of the immune suppression exerted by the virus above a certain threshold (5). Other stressors, such as neonicotinoid insecticides (6) or poor nutrition (7) can interfere with the system by impacting either directly or indirectly honey bee immunity.