The T-Virus is a failed experiment which was intended to create soldiers that could not be killed. Instead it turns them into mindless zombies which spread the virus through contact with their victim's blood. The G-Virus is a unique, advanced from of the T-Virus. It was created by Dr. William Birkin using a sample of his own DNA. He was working with Albert Wesker and planning to sell the G-Virus to a rival corporation. Umbrella caught wind of this betrayel and sent a team of soldiers to retrieve the G-Virus for themselves. Dr. Birkin was critically wounded during his encounter with the Umbrella soldiers, but he saved himself by injecting the G-Virus sample into his own blood. It transformed him into a powerful mutant, and shortly after he killed the soldiers and went on a rampage through Raccoon City's underground system. During his rampage, several people fell victim to his parasitic attacks. Soon after they were infected, instead of mutating, they would die from a creature bursting out of their bodies. This creature would grow into a large mutant resembling Birkin's mutation. However, on one occasion, Birkin's daughter Sherry fell victim to his attack. Because she has the same DNA as her father, the G-Virus would have bonded with her cells and transformed her into a powerful mutant, instead of it bursting out of her in parasite form. Fortunately, Sherry was saved from this fate by Claire Redfield, who gave her a vaccine to remove the G-Virus from her body. But after Claire helped Sherry escape from Raccoon City, she left Sherry in the care of the US government, so Claire could continue her personal mission to find her brother, Chris. However, Sherry was soon kidnapped by Wesker, her father's old partner, who intends to continue research on the G-Virus and it's effect on someone with Birkin's genes. Many fans believe that Sherry will emerge as the perfect carrier for the G-Virus in the forth-coming Resident Evil 5.