G-virus strand

The "G-virus", is the central plot point of Resident Evil 2. It is a highly advanced strain of the Progenitor virus with continuous mutagenic properties.

When Lisa Trevor, a test subject of the Umbrella Corporation, displayed unexpected immune resistance to the experimental NE-Alpha parasite, scientist William Birkin looked for a cause and found a primitive form of a new virus he called G-virus.

The G-virus greatly accelerates cellular duplication and revitalization, at the cost of higher brain function. The host exhibits animalistic behavior, loss of moral reasoning and memory, becoming driven by self-preservation and the urge to reproduce.

G-virus exhibits its symptoms within seconds, inducing repeated volatile mutations. A third eye on some part of the body was a typical feature of G-virus infection. The mutations become much more drastic when the host is wounded. William Birkin suffered five of these mutations, each more gruesome than the last, before his destruction.

The G-virus is only transmitted through implantation or ingestion, and cannot be passed through physical contact or injury. It can only be accepted fully by hosts with a suitable genetic makeup, such as a blood relative. If the host is compatible, the embryo begins to pupate and assimilate the host's body, turning them into a mutant of immense strength. The only known compatible hosts were William Birkin, his daughter Sherry and Curtis Miller. These hosts, called G-mutants, create their offspring by orally implanting small, parasitic "G-embryos" into a living host through the palm of their hand.

If the host has incompatible DNA, the G-embryo will rapidly grow inside the host's body, and will burst from their chest in a matter of minutes. It will then quickly develop into an adult "G-creature" and search for another host. G-creatures periodically emit more G-embryos.

The G-virus can be cured by DEVIL, an experimental vaccine. However, the vaccine is only effective during the initial stages of an impregnation-induced infection, before the embryos gestate. In the case of Sherry Birkin, DEVIL did not destroy the cells infected with the G-virus; it merely halted their spread, leaving her as a virus carrier.

In future games of the series, HUNK and Ada Wong procured samples of the G-virus for Umbrella and Albert Wesker, respectively.