Tyrant Virus, otherwise known as the t-Virus, is the general name given to a series of mutant Progenitor virus strains. Initially developed by Umbrella Pharmaceuticals in the late 1960s, the primary goal of the "t-Virus Project" was to effectively eliminate the need for a large-scale conventional army and generate revenue to go to their eugenics program, the Wesker Project. This required two things: the virus had to be highly-contagious to the point of infecting an entire target population and guarantee a 100% mortality rate. Such a virus was impossible due to such contagions' tendencies to kill too many people at once and prevent further spread. By 1978 development moved from creating a lethal, highly-contagious virus to one that would mutate hosts to become physically stronger and remain alive despite organ failures and severe brain damage, the latter leading to murderous aggression and an obsessive hunger to the state of cannibalism. With the 1981 discovery of a statistical 10% of any population is naturally immune, Phase 2 of the research project focused on creating workarounds. and the pioneering Arklay Laboratory team under Dr. William Birkin engineered a new species of animal that would hunt down and kill survivors, beginning with simple Bio-Organic Weapons such as the Web Spinner, but breaking ground with the genetically-chimeric Hunter α. In the mid-1980s, the t-Virus Project focused on creating intelligent bio-weapons, most famously the Tyrants. After the collapse of Umbrella in the early 2000s, the t-Virus became available to dozens of organizations with the means to finalize Umbrella's research in their own way and dominate the weapon industry. Independently developed mutagens such as t-Abyss were developed thanks to this.
From the Progenitor Virus' discovery in December 1966, the ultimate goal of Dr. Oswell E. Spencer and his colleagues Dr. Edward Ashford and Dr. James Marcus was the birthing of a new age of eugenics with mutagenic viruses improving the human race. To fund this program, dubbed the Wesker Project, it was agreed that strains of the virus should be engineered as a military product, leading to the creation of Umbrella Pharmaceuticals as a front for this research. Research on Progenitor strains was conducted simultaneously in different laboratories, with Ashford; Marcus and Spencer all engaging in independent research. t-Virus research began in the late 1960s, soon after Umbrella was founded.
Dr. James Marcus' research reached a breakthrough on January 13, 1978, which warranted his coining of the name "t-Virus" to divorce the strain from Progenitor Virus. The new strain mutated in the bodies of leech test subjects. Using the virus on humans saw a very different response compared with Progenitor infection, rather than dying the infected instead became aggressive, were found to have cannibalistic impulses, lost intelligence and suffered from significant necrosis.
The nearby Arklay Laboratory also worked on mutant strains of Progenitor and had done so since its opening with Progenitor "Type A" and "Type B" strains. In the 1970s they also used "t-Virus" as the name of their new strains. This team made their own breakthrough in 1978 under the leadership of Dr. William Birkin. Fascinated by Ebola's potential as a weapon, Birkin noted that people would be killed too quickly for it to work in war adequately. A modified t-Virus strain with RNA from Ebola was created, which led to their independent creation of Zombies. Spencer was, however, unsatisfied with the virus the Arklay team was developing, as approximately 10% of people were believed to be naturally immune to the new strain. To guarantee a near 100% success rate in battle, the Arklay team bonded a human egg and reptilian DNA through the virus in 1981, creating the "Hunter," a creature that would be used in battle to kill these remaining survivors. Because the t-Virus can make genetic recombination between different species comparatively easy, this virus was mass-produced within Umbrella and supplied to each research facility for new B.O.W. model development.
At some point, following this, the Arklay team began working on a new strain of the virus discovered in the body of a zombie. This strain enabled the "V-ACT" process, which mutated the bodies of unconscious zombies. Other facilities such as the later NEST experimented with a further mutation of this strain which mutated the infected into Lickers. As development moved on to realise the Tyrant Project, the ε strain was completed in 1998, which increased the chances of a Tyrant being successfully developed. The project was successful with the creation of the T-002, from which the T-103 models were derived.
A third group researching the t-Virus development was located in Antarctica, led by Dr. Edward Ashford and his son, Alexander. As Alexander was not a trained virologist, he was unable to lead the project after his father's sudden death. And research was effectively halted there for over a decade until the genetically-engineered Alexia Ashford developed a new t-Virus by infecting a queen ant with the Progenitor Virus, the queen itself already being infected with an ancient virus endemic to ants. Alexia went into hiding soon after infecting herself with the virus, and it was believed until fifteen years later that her experiments had failed.
New viral strains were developed towards the end of Umbrella's existence and the years following. One such version was the t+G-Virus, a t-Virus strain which was able to enhance infected bodies with the ability to discharge electricity. t-Abyss was created under the oversight of Morgan Lansdale, which grafted the genome of another virus onto a t-Virus strain. t-Phobos was engineered by Dr. Alex Wesker to trigger mutations in humans when it came into contact with certain levels of stress hormones indicative of fear. C-Virus was a heavily re-engineered strain of t+Veronica used by Neo-Umbrella in 2012 for bioterror purposes.
Like any other viruses, t-Viruses make contact with a cell's membrane and insert their genetic coding into the cell. The cell absorbs the viral genome into its own, which hijacks the cell's intended functions, using them to produce virions similar to the original. The new virions are then released from the host cell and infect the neighboring cells, which starts the process all over again.
Different t-Viruses can react in different ways to humans. Before 1978, the t-Virus simply killed people, but the independent accomplishments of Marcus' and Spencer's labs led to zombification as the typical outcome of infection. Higher brain functions among the infected almost cease entirely and zombies can only perform minor tasks such as turning doorknobs. It should be noted that while zombification is known to result in brain damage and necrosis, the hosts are not, in fact, dead, as the t-Virus is incapable of reanimating dead tissue. Even with a shut down of the respiratory and cardiovascular systems, or apparent brain death, infected people do not die. Since some of the traits of zombies are the decomposed skin and the lack of pulse, they are often mistaken for reanimated corpses.
In viral strains capable of the "V-ACT" process, unconscious zombies are known to mutate in an hour or so. Crimson Heads develop razor-sharp claws, sharp canine teeth and their hearts pump blood rapidly across the body, resulting in their crimson hue. Other strains instead create "Lickers," which are humans whose skin has entirely rotted away to show the muscles. Their brains are exposed, and they have powerful, long tongues that can be used as whips to attack people. An oddity of V-ACT is a creature known as "Suspended." Only one specimen of this creature is known to have existed. What it actually was is unknown, though it is possible to have been the result of a zombie ceasing its mutation mid-transformation.
There are rare cases where a human responds differently to t-Virus infection and transforms into a dominant mutant. These mutations are the result of unique genetic factors that only one in ten million people displays. People with this genetic quality were highly prized by Umbrella, as they could be turned into bio-weapons known as Tyrants.
The t-Virus is capable of various methods of subject infection. Research files supplied in the Arklay Laboratory identify the virus as having a protein structure.
Injection: Due to its importance in bio-weapons development, the direct injection of the virus into an organism's body was considered by Umbrella to be the "primary" means of infection.
Water: Arklay Dam and the Raccoon Sewage Treatment Plant were contaminated with the virus, leaking into the city's water supply as a result and infecting many civilians.
Direct Fluidic Transmission: Anyone attacked by an infected host in close combat, be it by bite, scratch, gash, or stab may have the virus transferred to their bloodstream via contact with infected bodily fluids and tissues. Umbrella Corp. believes this to be a secondary means of infection. It is not a precise form of infection, however, as dry bites are a possibility.
Airbone:: Evidence in the Arklay Laboratory and the Military Training Center indicates the t-Virus is capable of spreading as an airborne pathogen in unspecified laboratory conditions.
Prototype antibodies for the t-Virus were available to Umbrella staff, including mercenaries within the UBCS. However, due to the unstable nature of RNA viruses, these antibodies could not offer permanent protection. The staff at Incineration Disposal Plant P-12A transformed into Zombies when the virus they were constantly exposed to mutated significantly enough to cause the antibody to become useless. The consumption of certain medicinal herbs and regular anti-viral pills can slow down t-Virus mitosis temporarily.
A vaccine was created at the Raccoon General Hospital. Faced with infected patients flooding the wards, the staff desperately tried to create a vaccine to halt the outbreak. Though they were successful, the staff had transformed into Zombies before any of them could use it. The only known sample of the vaccine synthesized was used to treat former S.T.A.R.S. officer Jill Valentine, who had been infected by the Nemesis-T Type.
AT1521 was engineered by the staff of the Umbrella R&D Center in Raccoon City. Researchers Linda and Carter both tried to escape Raccoon City with this vaccine on October 1 with the hopes of replicating it later. The original sample was destroyed when the vial was destroyed by Tyrant R, though Linda was aware of how to create another.
The t-Vaccine was a commercial-level vaccine produced by the WilPharma Corporation to fight bioterrorism in 2005. All but one sample of t-Vaccine were destroyed in the act of sabotage by its creator, Dr. Frederic Downing, to ensure that only bioterrorists purchasing from him had access to it. He was arrested by the Harvardville Police Department before he could sell the sample.