> What is known about how the hive clears itself of [virus] infection... ?
> How long can the DWV, Nosema C. and paralysis viruses stay in the
> hive even with a newly mated, non-infected queen?
It's worse than you hoped, the short answer is "never gonna go away".
The only good news is that no one has ever seen a "bad case of DWV" without
a bad case of varroa.
These links are pasted from my bee class reading list.
TL;DR, these single-strand RNA "survive" intact for months of environmental
exposure, are essentially "ubiquitous", and are very portable.
The viruses of concern to beekeepers are easily found at low levels in even
"healthy hives". I think this was first realized in France, and has been
repeated with sharper tools several times, recently by Bob Currie in Canada,
who made some nice charts I use in talks:
https://www.cambridge.org/core/journals/canadian-entomologist/article/occurr
ence-detection-and-quantification-of-economically-important-viruses-in-healt
hy-and-unhealthy-honey-bee-hymenoptera-apidae-colonies-in-canada/F541AD2772E
090F4AF96D74AE74A762C
https://tinyurl.com/yaxxshfh
Judy Chen of the Beltsville Bee Lab found that bees were transferring
viruses to each other and their queens within the hive via mouth-to-mouth
feeding.
https://link.springer.com/chapter/10.1007/978-3-642-17815-3_6https://tinyurl.com/ydgvqwna
Penn State and Ian Lipkin presented evidence that viruses can be found in
pollen loads carried home by foragers who do not themselves have those
viruses. They speculate that the pollen is infected by feces from infected
bees.
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0014357https://tinyurl.com/yb9fnzcv
A group from Iowa verified that solitary bees carried honey bee viruses,
spreading even viruses that did not affect them.
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0166190https://tinyurl.com/ybh948h5
In New Zealand, what they call "Argentine ants" have been found to carry and
spread bee viruses
http://rsbl.royalsocietypublishing.org/content/11/9/20150610
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