http://www.sciencedaily.com/releases/2009/03/090313150254.htm

. Experimental research with insect larvae at Wageningen University and
> Simon Fraser University in Canada has shown that one virus particle is
> theoretically enough to cause infection and subsequent disease.


Gets back to the relationship of Varroa and virus. Before Varroa, it was
noted that there were virus in the colonies but they were more a lab
curiosity than a problem. Add mites and that changed dramatically. So you
can have a low threshold of virus to get fairly high infection rates - 20%
for low levels in the article. And once started, the levels increase to
epidemic levels and you lose the colony.

Bill Truesdell
Bath, Maine

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