The T-Virus is featured in the Resident Evil franchise.
A highly contagious virus, spread mostly through liquids such as bodily fluids and water, that causes cellular necrosis in humans and other animals, turning them into zombie-like creatures who are difficult to kill. It can easily mutate into other strains, some of which have mutagenic effects on the host. In insects or amphibians, the resulting mutation often involves increased aggressiveness, increased size, and (almost always) the development of poisonous traits.
In mammals, the results include aggressiveness, physiological changes of varying degrees, and an extremely increased evolutionary rate. However, it is shown that some humans can bond with the T-virus and its variants and gain heightened speed, strength and strange powers while retaining their personalities, as in the case of Albert Wesker and Alexia Ashford. Variants include the NE-T virus, along with many others.