Where in the world are you - the uptick relates to the season but I’m unsure which season your pointing to. I’ve inderstood it to be as follows: Treatment comes out as honey supers go on. Varroa numbers start to grow as brood area expands and more drones are produced (which they prefer). At the end of the season there are a lot of varroa but the brood area starts to shrink. This is disastrous for bees as the percentage of cells with varroa in them is now very high. Deformed wing virus et al start to become very obvious. This is probably the peak in varroa numbers that you refer to. Late autumn or winter arrive, bees are dying as the virus load is too high. Even treatment probably won’t work at this stage. The brood is now longer all covered and starts to die. Swarms happen as bees try to abscond from the dying colony.