lone is right and so treat it as you would any fungus.
i had it once bad enough to take down the hive. no other hive was infected and no measures i took helped until i read some obscure paper about raising the temp in the hive.
instead of ventilating as i had bee...thinking fungus like dark and moist, i closed all but a very small opening and got the temp up as high in the hive as the sun would allow. it really did seem to help a lot. unfortunately, we don't get the very high temps here...and you are heading into your fall?
that's the only thing i found that kind of worked...and then i bleach dipped all my comb and boxes after losing that hive eventually. reused the old stuff and never had a problem with it. don't know if i'd do that today, but didn't know any better then