Deformed wing virus (DWV) is an RNA virus, one of 22 known viruses affecting honey bees. While most commonly infecting the honey bee, Apis mellifera, it has also been documented in other bee species, like Bombus terrestris, thus, indicating it may have a wider host specificity than previously anticipated. The virus was first isolated from a sample of symptomatic honeybees from Japan in the early 1980s and is currently distributed worldwide. It is found also in pollen baskets and commercially reared bumblebees. Its main vector in A. mellifera is the Varroa mite. It is named after what is usually the most obvious deformity it induces in the development of a honeybee pupa, which is shrunken and deformed wings, but other developmental deformities are often present.