The disease is spreading quickly, there is no much time left. We got to do something about it, if we don't, everything will change and nothing will be as we remember.
A virus. That's all that they said it was.
It was simple enough at first.
You were infected.
You got a fever.
You died.
Nobody mentioned the part where you came back. And that's how it destroyed the world.
Well, most of it at least.