I also am interested in how it came to be that everyone is now infected. How can that happen? Was it a natural environmental trigger like that terrible M. Night Shamalamadingdong movie "The Happening"? Was it governmental experimenting with mass mind control like the conspiracy theories on chemtrails. Vaccines for viruses?
They never really explained that in the show or the comics. I wonder if they will ever explain it.
It was started by Walter White's blue meth.