n Wesker's Report, it is revealed that Dr. William Birkin gave Cpt. Albert Wesker an unnamed virus to use when he faked his death in 1998, and as a side-effect he receives superhuman strength and speed. It has no visible side-effects besides turning his eyes red but at times yellow. Technically, the virus has never been discussed in any Resident Evil game. However, Wesker's eyes do show the side effects of the virus in Resident Evil: Code Veronica.
The virus hastens the host's metabolism, giving it heightened strength, speed, and regenerative abilities. Unlike the other viruses featured in the series, it is not a severely mutagenic virus, and its effects are limited to muscle tissue and lower organs, leaving the nervous system untouched. Though Wesker is responsible for an impressive list of horrific crimes, it is unknown if the virus was responsible for his psychotic behavior, or if that was his natural disposition.
As a prerequisite to increasing the host's speed, the virus also affects ocular tissue, allowing it to view and process visual information at a speed allegedly equatable to raptors. This modification of the eyes is the only visible effect of the virus on its host.
