I saw an interview with Kirkman talking about the spinoff. He said it will be in the same universe as The Walking Dead, but it will give them an opportunity to build an new cast of characters and storylines apart from the comic inspired arc.

For example, we basically had to learn along with a comatose Rick the rules of the new world. How did society identify, respond and come to grasp with the new reality? How did society breakdown? I can see this series being set in more in the times of the societal breakdown as the Rick storyline basically bypassed all of that.

TS-19 explains about all enough that we need to know about the virus. Everyone is infected. Everyone reanimates without a brian or brain stem injury. I think it ruins it a bit if we know much more than that.