The Undead of The Trenches

During the German invasion of Russia, a mysterious disease arose after a battle using a high amount of chemical weapons. All soldiers who contracted the disease dropped dead in an instant, and the disease was assumed extinct. But after a while the corpses of said soldiers rose back from the dead, and the true method of its spreading was discovered. If a "inflicteds" as the soldiers call them, saliva makes contact with your blood stream, you become infected.