Many years ago, I read a short story whose premise was that Los Angeles was physically infecting additional territories, as though it were a virus. Heroic measures were taken to contain it, but in the last paragraph, a couple in the Midwest (possibly Iowa) succumb and start wearing sunglasses.
I have been searching for the story for many years, but with no success. I’m sure it was published well before 1970 (probably in the ’50s), and I think I read it in an anthology.
If you know this story, I’d be grateful for the details. Thanks!