High losses in the U.S. are mostly among hobbyist beekeepers who tend to purchase commercial stock that is then not treated for varroa and dies over winter. There have been some huge losses among commercial beekeepers such as Adee who lost @30,000 colonies one winter about 5 or 6 years ago. Survey the beekeepers who actually know something about beekeeping (winter preparation particularly) and who treat for varroa, most of them have winter losses less than 10%. So far this winter, I have zero losses.
I have not treated my bees since 2005. A couple of years ago, a research project in the EU cast a wide net for anyone who had long term survivor bees. Geoff Williams from Auburn University came up and took samples of 8 of my colonies. The results came back a few months ago showing that they did not find any of the known varroa tolerance genes. But and it was a big one, they did find that my bees show a box gene mutation that was highly concentrated in my colonies but is almost never found in commercial stock. The gene affects hair structure on a bee's body. He came back a couple of months ago and got a few more samples to see if they could track expression of this mutation in my stock. My only claim is that my bees are alive and thriving after 17 years with no treatments for varroa. I inspected a colony today that had 5 frames of brood and was hauling pollen in at a high rate. I'm sure I could find a few varroa with an alcohol wash, but equally sure that there are not enough to cause problems for the colony.
As I've previously posted, I am in a reasonably isolated area with no other beekeepers near enough to influence the local drone population.