The fun part about is that we as players never see it coming, if they could keep that element in it'd be great. (A year ago I believe it was a 911 call stating that a friend was not feeling well... this soon happened
I have no idea what the default one would be like, but anyways, yes one is in the works. Details will not be revealed until it's too late for humanity. All I can say at this time is, arm yourself and stockpile that ammunition.