We know it started in Asia, somewhere in India or Pakistan. A bunch of locals came down with some sort of virus that killed just about everyone who came into contact with it. Unfortunately, during the early stages, the virus was highly contagious and the infection was all but undetectable, so it spread fast. The later stages of it caused some sort of muscle contractions that looked like dancing, which reminded someone of a multi-armed Hindu god, and so it got named the Shiva Virus. Despite all the technology and wealth available, people died by the thousands. Then the nukes started going off. Not sure who started it or how, but within a few days, a good chunk of Southern Asia was irradiated wasteland. A couple of invasions and some more nukes later, and the whole world pretty much got screwed.
The beginning of the Fall is somewhat up for debate, but 2055 is the most common year cited. By the time the virus actually reached North America in 2056, war had broken out on the east coast between the United States Government and the Federal Emergency Management Agency, (which was supported by the United States military). By most accounts, the Fall was over by 2062, around the time of the death of the last President of the United States. At that point, every human being was locked away in some sealed bunker, an immune carrier of the Shiva Virus, or dead. It's estimated that less than one out of one-hundred people survived the Fall, and even that sounds generous.
Around here, we had some additional problems, seeing as how a few nukes had hit the region (not sure who sent them) and a lot of the old Rothium kegs that were being used by GlobalTech to generate power were busted. The way the Techs tell it, the kegs were supposed to use heavy water to provide power; when rainwater got in them, they just spewed radioactive nanites. Few folks have a clue what all that means, but it's obvious that radiation is still common throughout the region, and it does a good job of keeping people from reaching the outside world. There're all sorts of nasty critters and radioactive storms just outside the Province, and they're a good way to get yourself dead. For now, we're stuck in the Grand Canyon Province. It could be worse
Source: official Website