Necrosis

From Resident Evil Wiki

Necrosis is the name given to the unnatural death of cells and living tissue. It begins with cell swelling, chromatin digestion, and disruption of the plasma membrane and organelle membranes. When a person is infected with the T-Virus several side-effects show. If one finds the Keeper's Diary they will discover that before someone infected with the T-Virus becomes a zombie, Necrosis will take place.