Hi Bill
I don't know if I can properly explain the difference and the similarity of the viral strains. I have been reading but the stuff gets pretty hairy, it's almost like another language. They say

... data clearly showed that full-length VDV1 sequences were present alongside the full-length DWV, 
we also found strong evidence for VDV1-DWV recombinants ...
In future studies, additional tests will be necessary to determine the precise composition
of virus complexes containing DWV, VDV1 and their recombinants in individual honey bees rather that
pooled samples as in this study. Such VDV1-DWV recombinants pose an additional threat to US honey bees
because recombinant viruses of the same type, but generated from different parental DWV (DWV-A) and VDV1
(DWV-B) strains, are most virulent in the UK. Generation of VDV1-DWV recombinants suggests that the
VDV(CP) × DWV(NS) combination may have selective advantages over the parental viruses.

Ryabov, Eugene V., et al. "Recent spread of Varroa destructor virus-1, a honey bee pathogen, in the United States." Scientific reports 7.1 (2017): 17447.

¶

One of the problems is the shifting names. VDV1 is also called DWV type B, as explained here:

One virus in particular, DWV, is considered an important predictor of colony failure. Varroa destructor has altered the dynamics of DWV dramatically, reducing within-host genetic DWV strain diversity, and leading to the global spread and dominance of genetic variants related to DWV genotype A (DWV-A). We have recently shown that another recently described genotypic variant of DWV, genotype B (DWV-B, also known as Varroa destructor virus-1 or VDV-1, is more virulent than classic DWV-A

In a field study, we now find the prevalence of DWV-B, an emerging variant of DWV1, and V. destructor infestation to be highly correlated with overwinter honeybee worker loss. Low virus titres in bees surviving to spring further suggested that individuals infected with high DWV-B titres had died overwinter. To our knowledge, our study is the first to provide strong correlative evidence of this distinct genotypic variant of DWV and OCL in the absence of the classical DWV-A.

Natsopoulou, Myrsini E., et al. "The virulent, emerging genotype B of Deformed wing virus is closely linked to overwinter honeybee worker loss." Scientific reports 7.1 (2017): 5242.

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html