Oi, I'd totally neglected to think about migration, as well. Good thing it's only mammals who can catch the disease, otherwise birds would've brought it to every place in the world!
I'm trying to figure out how New Zealand would be doing... I think they're probably gone. All of those sheep, and they weren't listed as one of the nations that closed their borders early on like Iceland and Japan did.
And speaking of island nations and closed borders, have we discussed Madagascar yet? They're one of the first four to close their borders in the comic, but they're also not far from the mainland at all, and have tons of native mammalian species. Also, tropical climate. Probably totally overrun, yes?