Tank is a symptom combo exclusive to the Necroa Virus DLC which allows some zombies to greatly increase strength and body mass. Severity increases when this combo is in play. Anabolic Boost and Bone Dysplasia are required. The achievement Tank is earned for forming the combo.
- This combo may based on a type of zombie from Valve's Left 4 Dead franchise. The Tank in that game likewise has extreme muscle mass, giving him (tanks are exclusively male) high durability and decent melee power for their size, while still reasonably fast.