The War Z's name to Infestation: Survivor Stories, "in part to help fans differentiate the popular game from similarly titled brands," a press release reads. If we were to take a wild guess, that's probably in reference to DayZ, the Arma 2 mod that gained massive popularity and is due out this year as a standalone game.
"OP Productions initially filed The War Z trademark early last year, but soon found out from the United States Patent and Trademark Office that the name was comparable to another property," the statement says. "After months of trying to resolve the issue, OP Productions decided the best option to avoid confusion among players was to rename the game. Current players will not experience any change or interruption with the exception of the change in name and game logo."
The War Z launched on Steam on December 17, but was quickly removed for advertising inaccurate game elements. The War Z re-launched on Steam in February.