In Wesker's Report, it is revealed that Birkin gave Wesker an unnamed virus to use when he faked his death in 1998 at the Mansion Incident, and as a side-effect he receives superhuman strength and speed. It has no visible side-effects besides changing the colour of his eyes.. The virus speeds 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.. 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.. The virus is discussed in one of the files of Resident Evil: The Umbrella Chronicles. This file, called "Memo about Virus", explains that the virus is from the "mutation stocks". Requiring an injection of at least 5 minutes prior to use, 10% of subjects fail to revive, while 20% revive as they were originally and 70% revive with its beneficial mutations to the muscle system and circulatory system.