I'm looking for the name of a cartoon, but I only remember bits and pieces of it. In it half the planet (Earth?) is taken over by some sort of virus. The virus maintains geographic control of its infected with some sort of fog that is impenetrable or something.
The infected think it's wonderful, but of course the healthy people want to cure them or hold them at bay or something.
I know this was a thing; I just can't for the life of me remember what it was called.