[Crikey, does he need help? Oh wait, it's Billy. That might end badly.]

Well- I don't know that much more, honestly. But as far as I know everyone's gotten inoculated, and even if they haven't, there's a cure in case it comes back. I don't know about where it came from, but the people who weren't infected were looking for one guy from another enclosure who apparently got it first. Or was the carrier, or... I don't know. Really, the details are kind of unclear. You'd be better off talking to one of the doctors who made the cure.