> From the report it seems as if AFB was present and latent...?

Assuming that the same test method was used, the report made a very strong case for a quick spread:

a) supers and frames put onto 20 AFB-free colonies the next spring. 
b) The 20 colonies were placed in an apiary with a further 20 colonies that did not receive such supers.
c) There were no obvious symptoms of robbing when the supers were placed on the colonies. 
d) However, samples of bees taken from each hive TWO DAYS LATER all tested positive for AFB spores, including those from the colonies that did not receive AFB supers. 
e) Four (20%) of the colonies that didn't receive wet supers, and 9 (45%) of the colonies given infected honey supers, developed AFB infections.

Could this all be coincidence? Sure, but the "two days later" is the clincher to me.

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