User blog comment:Spawny0908/UPDATE!!!!: The Free DLC pack is coming in...../@comment-3563546-20110907151828/@comment-2086180-20110907155652

Old undead overrun is as it was at release, new undead overrun is after an update, with slower spawning zombies, exploding wretcher spit in sudden death and smaller boundaries. The new patch will hopefully restore the original settings