To treat or not to treat for mites: https://youtu.be/Ce1bIvBCwkk
I recommend you treat or make sure you know what your levels are.
H2 overwintered really well with 16 frames of bees and some signs of early brood rearing starting in February. Mite levels last fall were low ~34 mite drop after an OAV treatment. 
This hive collapsed in late June 2020 after having a great spring ramp up. I re-queened it and made a split off of it. This is the hive that had bees behaving like they were poisoned. I thought maybe it was due to Death Camus pollen/nectar (timing with bloom). I noticed the same again this morning. This hive has had a mite drop of ~650 mites in the last 7 days post OAV. Assuming 95% efficiency and that 50 to 80% of the mites are in the capped cells. The mite number would be in the 1,500 range. This hive has 20,000 to 30,000 bees (single brood). That would make the infestation level 4% to 7%. Way too high. The attached video will show a sick bee with an attached mite walking in circles with its tongue dragging on the landing board. And other bees trashing about. I will continue to treat this hive until the phoretic mite numbers drop significantly. This goes to show how assuming and not taking action earlier may have put this hive at risk. We've had a cool wet summer with about 1/3rd of the typical forage hours. Booming pollen flow early in the season that exploded the bee populations followed by wet cold weather leaving the bees hive bound.
"(For the record, “phoretic” is not the correct term to apply to varroa mites, because it implies the mites are simply hitching a ride without doing harm to the bees. The more accurate term is “ectoparasitic,” which applies to parasites that are on the outside of their host. I’m making an effort to replace “phoretic” with “ectoparasitic” in my personal lexicon, but I understand a vast majority of beekeepers only recognize “phoretic” in relation to mites.)" Source: https://www.mitecalculator.com/

With a bit of digging I found this: "Acute Bee Paralysis Virus (ABPV)
Acute bee paralysis virus was accidentally discovered when CBPV was first isolated. ABPV displays similar symptoms as CBPV however the acute adjective describes a bees’ more rapid mortality compared to CBPV. Unlike CBPV, ABPV virulence is directly related to Varroa infestation. APBV is transmitted in larval jelly from asymptomatic infected adult bees to developing larva or when vectored by Varroa mites to larvae and pupae. ABPV is common and typically cause covert infections (no obvious symptoms) when transmitted orally from adult to developing bee. It takes about one billion viral particles to cause death via ingestion, but when vectored by Varroa and directly injected into the developing bee’s hemolymph, only 100 virus particles will cause death (Genersch & Aubert 2010). When the virus is picked up by Varroa, the transmission rate to pupae is between 50 and 90 percent. The longer the feeding period of Varroa, the greater the transmission rate will become. (Genersch & Aubert 2010). Pupae infected with ABPV die before emerging, making the appearance of paralysis symptoms less obvious. The decline in emerging bees causes a colony to dwindle towards collapse. A colony infected with an ABPV epidemic will die within one season (Sumpter and Martin 2004)." Source: https://bee-health.extension.org/honey-bee-viruses-the-deadly-varroa-mite-associates/

Etienne
Yukon Territory

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