Plague Zombies are victims of a virulent and deadly infection spread by the minions of Nurgle. Not only do they die as the result of the disease, they return as undead, mindlessly devoted to adding their former comrades in arms to their number.
The Zombie plague (the "Curse of Unbelief") has been making its way around the 40K universe for quite some time, from the underhives of Necromunda to the furthest corners of the Segmentum Obscurus.
Plague Zombies act very much like the zombies in films of today, mindless, shambling and cannibalistic. The main thing about plague zombies (and zombies in general) is that they are hard to kill and require an accurate shot to the head to kill them.
Quote:
"Throne, don't they ever stop?' Gasped Torgaddon. ' I must have killed a hundred or more of the damned things.'
You probably keep killing the same one, replied Loken, 'If you don't destroy the head, they get back up again."1
Source
- 1:False Gods by Graham McNeill, p.149