The G-virus (also known as the Gene Virus) was one of the most potent creations of Umbrella, and the pet project of Dr. William Birkin. It was capable of inflicting radical changes within the body of any organism that it infected. In short, it was considered by many to be the ultimate biological weapon at the time of it's creation. Research and development into the virus was halted due to the calamity that ensued following the Raccoon City incident, however the T+G-virus variant was created in an effort to control the erratic and volatile effects of the G-virus.
History
Discovery
The G-virus was the byproduct of years of research and hard work by William Birkin. Birkin had discovered the virus along with Albert Wesker while they were both chief researchers at the Arklay Research Facility. When they implanted Lisa Trevorwith the NE-alpha parasite that they had acquired from Umbrella Europe, the organism was absorbed within her body and no visible effects were immediately noticable. Intrigued by this development, the two researchers ran a series of tests and came across a startling discovery - the basis of which would later become the groundwork for the G-virus.
Research and Betrayal
With his research on the T-virus completed, Birkin immediately went to Umbrella and requested his own facility, equipment and personnel so that he could begin work on developing and refining the G-virus. In 1991, the G-virus project was authorised by Umbrella and Spencer soon granted Birkin the assets he requested. Work soon began on the construction of an underground research facility beneath the outskirts of Raccoon City. It was here that Birkin carried out the remainder of his research on the G-virus. Over the course of the next seven years, Umbrella began to grow dissatisfied with Birkin and suspected that he might be planning to betray them. To rectify this, Umbrella ordered the Umbrella Special Forces, Alpha and Bravo teams, to recover a sample of the G-virus.
It is important to note that Umbrella Europe was the branch responsible for the attempted forced acquisition of the G-virus, most likely due to the rivalry that existed between the European and American branches. During the raid on his laboratories, Birkin was mortally wounded by stray gunfire. As his wife Annette rushed to find medical equipment to treat her dying husband, Birkin injected himself with the G-virus and became his own life's work - the creature known as "G", or officially referred to as a "G-Type".
Traits
Upon injection, the G-Virus causes systemic biological changes resulting in accelerated tissue growth and emergence of new traits. This accelerated growth facilitates the regeneration of damaged tissue, allowing the subject to survive even otherwise-lethal injury; however, this growth also causes development of unusual features such as extra eyes and limbs, and ultimately, metamorphosis to a completely non-human form.
An infected subject can transmit the virus to other individuals; however, the virus cannot be transmitted in its pure form like the T-Virus. Transmission seems to occur through forced embryo implantation, which leads either to complete replacement of the host's cells, or yields a malformed, incomplete creature which hatches from the host's chest. Success of the process depends upon the new host possessing blood ties to the original host, which is why Birkin hunted down his own daughter, Sherry, so as to implant an embryo into her. Any other attempt at embryo implantation leads to the new host rejecting the embryo which by this time had fed off of the host for a time long enough to sustain itself. At this point, the G-virus forcibly mutates the creature and the result is a grotesque monster that is much weaker in comparison to a proper "G" creature. This creature can also spew out G-Embryos, however these embryos lack any ability to reproduce and are merely to aid in combat.
Another trait of the G-virus lay in it's difference from the T-virus. While the T-virus increases the metabolic rate of an organism while eroding many of the cells of the host, the G-virus revitalises these cells leading to the complete rebirth of a dead host eventually leading to the creation of a new creature entirely.
While the G-virus excels in brute force in comparison to other viral agents, producing a B.O.W. of immense power, the virus did have an Achilles Heel preventing it from being applied in future efforts. While the T-virus would largely produce the same results in a human organism, a zombie, injection of the G-virus would provide erratic, volatile and unpredictable results. As well as this, the speed of reproduction and mutation cannot be calculated. The only known physical trait of the G-virus that is prevalent in any host infected with it is the production of a huge eye in the right shoulder of the organism. Beyond this, no G-Type creature is identical due to the virus' erratic nature.
Another weakness of the virus which prevented it's proper application as a weapon lay in it's volatile nature. Hosts infected with the G-virus generally maintain no intelligence beyond basic instincts brought on by the virus, and the constant mutations a host goes through following damage usually leads to a devolution to a giant mass of flesh. In order to rectify this issue, Umbrella Europe sought to control the volatile nature of the G-virus by combining it with a T-virus antibody. The result was the T+G-virus.
Treatments
DEVIL
A single vaccine exists in the case of accidental embryo implantation, developed by William Birkin as a precaution. This vaccine was codenamed "DEVIL" and was co-developed with the G-virus itself in Birkin's underground research facilities. After impregnation by the G-virus, Sherry Birkin became the first known recipient of "DEVIL". It is important to note however that the vaccine does not eliminate the G-virus itself, but rather suppresses the effects of the infection.