I found the paper by L. Wilfert, et al. of interest.

2016. “Deformed wing virus is a recent global epidemic in honeybees driven by Varroa mites.”  Science. 351(6273).  http://science.sciencemag.org/content/351/6273/594

“In addition to the presence of DWV in Varroa-free populations, the phylogenetic reconstruction also contradicts Varroa as the ancestral host of the virus. The ancestral host is unambiguously identified as A. mellifera (state probability PLp = 99.43%, PVp3 = 97.18%, PRdRp = 92.7%) and not V. destructor (Fig. 1) or A. cerana (figs. S6 and S7). The geographic origin is less certain, with ancestral states being reconstructed with low probabilities (Lp fragment, East Asia, PLp = 69.77%; Vp3 and RdRp fragments, Pakistan, PVp3 = 77.25%, PRdRp = 54.84%). Although we cannot categorically rule out the possibility that DWV was introduced to honeybees from an entirely unknown host, this pattern does rule out Varroa and A. cerana as the ancestral DWV hosts.

The most parsimonious explanation for the phylogenetic pattern is our second scenario: DWV is an endemic honeybee pathogen that has recently reemerged through ecological change and the spread of Varroa as a vector, alongside increased Global movement of infected bees or other contaminated material, such as pollen. This conclusion supports previous work that postulated that the ancestral form of DWV may have been associated with A. mellifera (32) and that similarities between DWV lineages may represent a recent introduction from A. mellifera into other Apis species” (pp.595-596).

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