A world ravaged by a deadly virus, the Gamma Strain. Commonly known as “the sickness“, it is an infectious disease caused by a mutation of the influenza virus.

Vyal Pharmaceuticals was tasked to create a vaccine to stop the spread of this vicious virus. Phase I initial test subjects were shown to have a 100% recovery rate, and an end to this global pandemic was in sight. Standard precautions were ignored due to the spread of the epidemic, pharmacovigilance was ignored due to public outcry, and the a last minute stabilizer antigen was introduced into the production of the Phase III clinical trial antigen.

This "botched batch" was either a fluke or was manipulated by someone; which led to zombification.