https://www.scientificamerican.com/article/hantavirus-found-in-shocking-number-of-pacific-northwest-rodents/
Not surprised.
The hanta issue in Yosemite wasn't that suddenly there were a lot of rodents with hanta, it's more that human behavior changed.
Although... years ago they did take all brooms out of tent cabins to keep people from sweeping. But I wonder whether people just got hanta in the 1950s and nobody knew what it was.
Maybe like Lyme where so many cases were undiagnosed in the past.