This article, lately in the American Bee Journal, talks about untreated bee colonies (feral) developing resistance to DMVirus and varroa mites, and surviving into winter as well or better than treated colonies. Interesting.
What Can We Learn From Feral Honey Bees? - American Bee Journal
https://americanbeejournal.com/what-can-we-learn-from-feral-honey-bees/
Thomas Sealy has written quite a bit about feral bees and how they are surviving with varroa without treatment. Reading between the lines it seems they are small colonies and frequent (often bi-annual) swarmers. Not the type of bees that many want to keep.
A study in France showed showed that untreated bees could survive without treatment but.....the important bit for the beekeeper was when they were treated for varroa these hives brought in nearly double the amount of honey as their untreated counterparts located in the same apiary.
https://hal.archives-ouvertes.fr/hal-00892292/document#:~:text=Our%20results%20clearly%20show%20that,survived%20more%20than%2011%20years.