You ask a very specific question Therese.  Only some of the roughly twenty
known viruses that affect bees are known to be transmitted by
varroa--notably DWV and the paralytic viruses.

Pete already cited studies that found that virions could remain viable in
combs without bees.  However, DWV is ubiquitous in bees, so inoculum in
combs may be relatively unimportant.  And Bailey found that it is difficult
to infect bees with paralytic viruses via feeding (although I found that it
is quite possible with IAPV if the titre is high enough).

That said, in my own practical experience, restocking the previous autumn's
deadouts from the varroa/virus complex with bees the following spring, does
not appear to be problematic--those colonies appear to develop normally.

-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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