In the remake version of the game, the dead zombies will come back to life with increased speed and damage. This can be avoided by burning the bodies. To do this, you need a lighter and kerosene. Kerosene can be obtained from gas tanks. If the message is still appearing, even if you have the mentioned materials, just continue to play the game. You should be able to find a note in the room with the canteen that will explain all this.