Here is an interesting map of the spread of vorroa starting in 1904;
http://www.geocities.com/RainForest/Vines/9167/varroa.htm

Their original host was Apis Cerana, they spread by hopping from one bee to
another while foraging, from drifting Drones and workers, and from other
bees crashing from infestation and then them entering other hives. I am sure
there are other ways for their spread that others will mention. The bees
with no mites are in areas that are isolated and the mites have not yet been
introduced by infested hives being moved in by migratory beekeepers.
Migratory beekeeping was and is a major cause of spread along with package
bee shipments.

 . ..   Keith Malone, Chugiak, Alaska USA, http://www.cer.org/,
c(((([ , Apiarian, http://takeoff.to/alaskahoney/,
http://groups.yahoo.com/group/akbeekeepers/ ,
http://groups.yahoo.com/group/Norlandbeekeepers/ ,
http://groups.yahoo.com/group/ApiarianBreedersGuild/

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