Here in Florida, due to yearly inspections, we only get 1% of the hives inspected with AFB. This is pretty amazing considering that a large percentage on the commercial hives spend time, usually during the winter, here in Florida. Most get inspected shortly after arriving. .
The only case that I know of here in Florida was my buddies daughter bought 3 hives from a commercial beekeeper who was probably treating his hives on a consistent basis. Three years later, our Inspecter burned all three hives.
Jim Altmiller