It is very common on the Indian reservations, and when I was living in California in the 1990s, they had a hanta scare out on one of the Channel Islands that was popular with campers and hikers, so they closed it for a while. The rat/mouse feces dries up and goes airborne like a powder in arid/dry/desert environments, so you can catch it that way. Didn't they claim that was what killed Gene Hackman and his wife?
Maybe one day I'll tell the story about having coffee in the economy galley when my co-worker opened a fresh carton of milk (catered out of Chicago) to pour into her coffee and a rat's foot fell out into her cup. I wish I was kidding about that... I had the jeebies upon the heebies about milk cartons after that.