The War Z has had a pretty bad rap since it launched on Steam with a list of falsified claims about itself. In fact, the number of inaccuracies on the store page were enough of an issue for Steam to remove the game from sale for a while. It of course came back and still nurtures a fan following.
If you ever felt that the game's name was too similar to an other zombie survival game (DayZ) or a book that is about to become a motion picture (World War Z) then you'd be right. When OP Productions attempted to get the trademark for "The War Z" they were told the name is too similar to other trademarks.
As such, the developer has christened the game Infestation: Survivor Stories. The change is in name only and doesn't coincide with any game updates. You'll see this reflected when looking on Steam or at the official website.