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.
Fallen Earth requires a Mobility Radeon HD 3870 x2 graphics card with a Core 2 Duo E6550 2.33GHz or Opteron 180 processor to reach the recommended specs, achieving high graphics setting on 1080p. Minimum RAM requirements are 2 GB system memory. In short you need a 13 year old PC for best Fallen Earth performance.