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Mainstream universe
(Capcom's primary storyline)

"t" virions through a microscope.

The t-Virus (also known as the Clay virus ε-strain and the tyrant virus[1]) is a mutagenic virus created by the Umbrella Corporation. It was derived from the Progenitor virus and designed to take advantage of its mutagenic properties for the development of a new form of biological weapon known as "B.O.W." (Bio Organic Weapon), a living creature genetically modified for use as a killing machine.


Initial development

On December 4th, 1966, the Progenitor virus was discovered by an expeditionary team led by Oswell E. Spencer and James Marcus.[2] These gentlemen, along with Edward Ashford – a fellow aristocratic friend of Spencer – held a certain economic position and decided to begin research upon the virus. Most of the research was carried out by Marcus, after Ashford died in July 1968[3] and Spencer was already occupied by his burgeoning pharmaceutical corporation, Umbrella.

The Umbrella Corporation used its finances to secretly develop the virus under the radar of international authorities. In time, Marcus further evolved the virus, creating the first effective bio-weapon to be produced in large quantity and be closely studied by the Umbrella Corporation. By adding the virus to leeches, the attributes of both were combined, and the first primitive strain of the t-Virus soon saw the light in 1978.[3]

Research into weaponry

Though most of the research for the virus took place within the Arklay Laboratory underneath the Spencer Mansion façade, some eight miles northwest of Raccoon City, and the Umbrella training facility under Marcus' orders, covered by the American Umbrella offices, Spencer's Umbrella empire in Europe raced against Marcus to adequate the t-Virus to create a virus with an even greater destructiveness. Marcus' dreams to overthrow Spencer and his attitude towards the virus as a "money-spinning tool" for Umbrella were never fulfilled, as he was murdered before he could enact them. Birkin came to be known within Umbrella circles as the true creator of the t-Virus.[4]

During those years, vast numbers of t-viral strains were developed in the Arklay Laboratory, and tested upon one solitary test subject: Lisa Trevor. For years, she was subject to intense biological torture, which, despite all odds, she survived.

As well, William Birkin, grown conceited as being credited as the creator of the t-Virus,[4][5] spawned a myriad of biological weapons to serve as backup to the virus, to ensure a 100% death ratio in any populace the virus should be released. Among these are the Hunters (created by fusion of a human fertilized egg with t-Virus infected reptilian DNA),[6] the Ivies (flowers grown to unnatural proportions and given animal instincts, locomotion and rudimentary defense mechanisms),[citation needed] the Chimeras (a mixture between a fly and human given vague humanoid appearance, increased size and mass, improved claws, and better reflexes),[citation needed] the Cerberus (infected dogs - specifically Dobermans), and most importantly, the crowning achievement of Birkin's career for the time: the Tyrant.

Later, Lisa Trevor's body had deteriorated to inhuman levels. Birkin decided to implant her with the genetically engineered parasitic organism NE-α Type reputed to kill all its hosts, no matter how strong, within five minutes of gaining control over them.[6] The results astounded even Birkin: Lisa's body absorbed the parasite. Birkin's further examination revealed a heavily altered strain of the t-virus which had evolved over the course of 21 years since she was first injected with the TYPE-B strain of the Progenitor virus. He named this new virus "G" for "God" and began preliminary research towards the advancement of a new virus development project.

Use on the black market

In 1998, a series of biohazard outbreaks involving the t-virus began to occur. Several outbreaks were caused in the Arklay Mountains region due to the machinations of the Queen Leech, which had bonded with the DNA of James Marcus and became a veritable clone of the former scientist. For more than three decades, the t-Virus threat had been averted, but at the time of his awakening, the Arklay woodland was slowly corrupted by the infectious agent. Before long, the Arklay laboratories had fallen. The Laboratory was seemingly infected by infected water, causing its employees to fall to anarchy over the relatively long period of time between May 11[7] and late June, 1998.

From there, stories started stemming from the forest; several killings took place and an advance party of an elite paramilitary unit -, the S.T.A.R.S. Bravo team - was sent from Raccoon City to destroy the threat, oblivious to its real cause. Only four of these members, Rebecca Chambers, Enrico Marini, Kenneth J. Sullivan, and Richard Aiken survived the night. All of them had holed up in the massive mansion and its adjacent areas. The next evening, the S.T.A.R.S. Alpha team sought refuge in the mansion as well, after losing a man to an attack by the multitude of cerberuses, mutated Dobermans, which infested the grounds.

Later on, the remaining members of S.T.A.R.S. met up at the underground laboratory where the Tyrant (T-002 Type) was kept. This Tyrant killed Albert Wesker temporarily, and was killed by a rocket blast in a skirmish with the remaining S.T.A.R.S as it attempted to foil their rescue by returning Alpha team pilot Brad Vickers.

After the demolition of the manor, the virus sources were thought stopped definitively, but when William Birkin's subterranean laboratories were attacked by Umbrella's Black Ops in September 1998 in an effort to retrieve his G-virus, another outbreak ensued. This infection encompassed all of Raccoon and ended in the forced termination of the entire city. Umbrella was immediately exposed as creator of the virus due to the enormous amount of evidence produced from the scarce survivors, and was systematically dismantled and shut down.

Still, another outbreak was induced in late 1998, on Rock Fort Island, this time by the revived Albert Wesker and his new employers, referred to only as the Organization. This ended in the partial demolition of the Umbrella installations there and the total destruction of the South Pole Umbrella Research Center.

Yet another occurred in 1998, this time on Sheena Island; an Umbrella-owned "Tyrant Plant". Hundreds of adolescents from across the globe were kidnapped and taken there to be dissected, to retrieve a hormone important for the psychological development of the Hypnos-T Type.[8] This infection was caused by the - now mad with power - commander Vincent Goldman. The island was "sterilized" when facility's self-destruct system was activated.

Another occurred in 2002 on an Umbrella-owned luxury liner, the Spencer Rain, which was caused by an ex-Umbrella researcher-turned bio-terrorist named Morpheus D. Duvall, who was fired after the company used him as a scapegoat for the disaster at the Arklay facility.[9][10] The ship's crew and its passengers were transformed into zombies, or were killed by the B.O.W. specimens prepared for auction and display purposes. The liner was destroyed when it crashed into an island which housed the -also infested- Umbrella Waste Disposal Facility.

Also in 2002, an Amazonian organ-trafficking crime syndicate got hold of "t" and the similarly named, but otherwise unrelated, "t-Veronica virus". Receiving "t" and B.O.W.s through a dummy company of the Russian branch of Umbrella, the syndicate's leader, Javier Hidalgo, armed his organization with biological weapons. He also purchased t-Veronica through Albert Wesker, and proceeded to use it to treat his daughter from the same illness as her mother. After his daughter ran off, Javier, in a fit of rage, released the t-Virus throughout the surrounding area. The virus spread to at least two villages, transforming their inhabitants into zombies. Leon S. Kennedy and Jack Krauser ended Javier's rule with the assistance of his daughter.

A bioterrorist attack in 2005 India was halted by WilPharma Corporation's t-vaccine. This attack was actually planned by a WilPharma Corporation researcher, who wanted to demonstrate power of the virus and its vaccine to potential buyers on the black market.

Another outbreak occurred in 2005, within the Harvardville Airport, where the infection began after a single zombie entered the building and began to attack people within the building. A small-scale outbreak happened at the nearby WilPharma Corporation bio-dome facility, after a bomb was detonated. Both facilities were eventually sterilized, however.

The last known outbreak occurred in 2010, in Philosophy University, Australia where Rebecca Chambers was teaching as a guest lecturer. The BSAA forces stopped the outbreak from spreading further.

Then sometime after the Raccoon City outbreak a series of bioterrorist attacks started happening all over the world and so far the virus used in said attacks was the t-virus.

Development timeline

  • September 19, 1977: Marcus confirms the existence of the t-Virus.[11]
  • February 3, 1978: Marcus begins his experiment on leeches by infecting them with the Progenitor virus.[12]
  • October 23, 1978: Marcus ceases experimenting on rodents, citing humans as being the perfect guinea pig to prove its abilities.[11]
  • January 13, 1979: Marcus ends his research with the Leeches.[11]
  • January 31, 1979:see February 11
  • February 11, 1979: Spencer has employees steal Marcus' research.[11]
  • 1988: Marcus is assassinated and credit for the virus' creation goes to his student William Birkin, who was a conspirator.[13]
  • 1993: An experimental oncolytic virus treatment based on the t-virus, designated "T-JCCC203", is used in illegal medical experiment trials.
  • 2002: A hybrid strain of the t-virus and G-virus is created. The virus is named "t+G".


These are the following list of biohazard incidents involving the t-Virus. There are other small scale outbreaks in other parts of the world but information of them is unavailable.


Effects of Infection

The t-Virus is built like many viruses, as the virus makes contact with a cell's membrane, it inserts its genetic coding into the cell. The cell absorbs the viral genome into its own genetic make-up, which takes over the cell's functions. The cell begins to produce offspring of the original virus. The new viruses are then released from the host cell and infect the neighbouring cells, which starts the process all over again.[14]

The t-Virus can only properly function by consuming the cell in order to produce its energy. This slow breakdown of cells leads to the gradual breakdown of the host, causing necrosis. The virus incorporates itself into the host's DNA, which substantially alters it. This is why creatures, such as bees and spiders, only have very minor mutation, such as increased size, when compared to the human mutation caused by the virus.

Should the human host be alive at the time of t-Virus infection, all higher brain functions are destroyed. This leaves only the brainstem to govern behaviour. This leaves the infected host with a very animalistic behaviour. As the virus spreads, it damages the hypothalamus. This produces a massive flood of neurotransmitters, enzymes, and hormones such as norepinephrine and dopamine. These effects, combined with the painful symptoms of the infection, induce a psychotic rage, persistent hunger, and increased aggressiveness in those infected.

Should the human host be dead at the time of infection, only enough energy is produced to power the lower brain functions. These functions are responsible for the most primal instincts, such as walking and eating.

In either case, their late-stage appearance and behaviour are characteristics of their name-sake, a zombie.

Should a late-stage human host be rendered unconscious, the body will lay in a dormant phase appearing to be dead. In actuality the host is rapidly mutating due to the t-Virus becoming hyperactive. Within the time frame of an hour, the decayed skeletal and muscular system is reconstructed into a stronger and more durable form. Development can be seen of sharp canine teeth and razor claws, fresh blood seeps into remaining skin giving it a reddish hue, advances in decomposition, and intact eyes become a bright white. Umbrella researchers at the Arklay Laboratory have dubbed this stage "V-ACT", referring to the resulting creature also known as a "Crimson Head". To awaken, the brain must be jolted back to consciousness with a slight but important increase in intelligence, and large increase in agility and aggressiveness. As a consequence of this rapid mutation, cellular breakdown hits a critical point where the host cannot regenerate properly and can be killed permanently.

Depending upon the strain, the V-ACT may have different results. In the strain released in Raccoon City, most V-Acts usually resulted in creatures named by RPD staff as "Lickers". Which are completely blind and use their hearing to detect prey. At which point, they use their long tongues to strangle, impale, or decapitate their prey. At close quarters they also have sharp claws to slash their prey. Lickers may eventually evolve into a more advanced stage with larger claws. Lickers have exposed brains which serve as a weak point.

An oddity of V-ACT is a creature known as "Suspended". Only one specimen of this creature is known to exist. What it actually is, is unknown. It could be an in-between stage of a zombie and Licker or some kind of rare mutation V-ACT takes on. If it is a zombie partially evolved into a Licker, it would account for why its unable to spear prey with its tongue. It's only capable of grabbing its prey and using its tongue as a whip.

There are rare cases where a human genome can stably splice with the T-Virus's genetic material. The probability of an average human having this reaction, when exposed to the T-Virus, is approximately one in ten million. The result is a humanoid creature called a Tyrant. These creatures inherit all the enhancements of the Tyrant Virus, while lacking most of the degenerative weaknesses that result in zombies. They posses enhanced skeletal-muscular frames and superhuman strength, speed, agility, and durability, while still retaining enough intelligence to follow orders and carry out missions, making Tyrant's effective B.O.W.s. However, if a Tyrant's biological functions become unstable, it can undergo a secondary metamorphosis into a Super Tyrant. This transformation is analogous to V-Act in zombies, that results in Crimson Heads and Lickers. The subjects undergo greater bone, muscle, and cardiovascular growth and may develop features such as claws and an exposed heart. Super Tyrants are significantly harder to control, so this transformation is not preferred. To act as a failsafe, many of the mass-produced Tyrants are equipped with a Power Limiter, a device that stabilizes its biological functions and prevent the creature from accidentally becoming a Super Tyrant. If the device is destroyed however, nothing will stop the transformation from happening.

Wesker notes that he observes similarities in the apparently random mutations endowed by the virus (as examples he mentions the mutations undergone by Sergei Vladimir and what he knew of James Marcus' mutations) and explains he believes that the host's mindset is a crucial factor in explaining the mutation (e.g.; Vladimir becomes what Wesker calls "a monster whose very body is the picture of suffering", revealing what Wesker considered to be Vladimir's true self, and the rejuvenation experienced by Marcus, an aged man who understandably desired control and the restoration of his vibrant youth, characteristics that were carried to his own eventual mutation, including his true madness and the horrific mutation that overcame him in the end), and briefly wonders where does this theory fit with his own mutations.

Means of infection

The t-Virus is capable of various methods of subject infection. Research files supplied in the Arklay Mountains facility identify the virus as having a protein structure. As such, it is likely that any known methods of viral of Umbrella's experimentation (known as Bio Organic Weapons) with the t-Virus were initiated by direct injection of the virus into the host. This was considered Umbrella’s primary means of infection.

  • Water: In the initial outbreak at the Arklay Laboratory, the above-ground scientists and researchers were infected once the t-Virus contaminated the water supply. Similarly, Arklay Dam and the Raccoon Sewage Treatment Plant were also contaminated with the virus, leaking into the city's water supply as a result and infecting many civilians.
  • Air: The t-virus in its original form is an airborne virus, but upon infection of an organism, it mutates into a form spread via skin and fluid contact.
  • Direct Fluidic Transmission: Anyone attacked by an infected host in close combat, be it by bite, scratch, gash, or stab will 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. For story purposes, however, most of the main characters in the games were never canonically bitten or stabbed, though even highly infectious real world viruses do not always infect the victim after one exposure (but given the relentless attacks of those infected, one exposure might not necessarily mean a single scratch or bite). A "Dry Bite" is possible as well, so anyone bitten has at least a 1% chance of not getting infected. Evidence for this can be seen when an Eliminator bites Rebecca Chambers during a cutscene in Resident Evil 0.

Known Treatments

There are four known serums that will cure those infected by the t-Virus, but only in its earlier stages, before it becomes completely active.

Raccoon General Hospital vaccine

The first is an unnamed vaccine developed by doctors at Raccoon General Hospital[15] as a last-minute effort to halt the rapid spread of the t-Virus. However, most of the hospital's staff had already succumbed to infection before the vaccine could be properly produced even in small amounts.

This vaccine could be cultivated by using a specialized synthesizer and inserting a medium base into the system, then combining the necessary chemicals using the control panel. The exact components that were used to create this prototype are unknown; as most of the documentation regarding its production were either stolen by Nikolai Zinoviev or destroyed after Nikolai used C-4 to demolish the hospital, taking with it any evidence of the Umbrella Corporation's involvement with the hospital in the process.

However, Carlos Oliveira was able to create a single dose of the vaccine for Jill Valentine and managed to escape moments before the hospital's destruction.[16] While the vaccine apparently did not immediately cure Jill of the virus, it did send it into hibernation, until it eventually died out. It also apparently created powerful anti-bodies within Jill, making her immune to most other viruses, even possibly Uroboros, another virus strain extracted from the Progenitor Virus.


Daylight was developed by Greg Mueller and Peter Jenkins of the Raccoon University.[17] The actual ingredients for Daylight are:

  • P-Base - an unknown chemical liquid that requires preparing before being mixed. Once all the ingredients have been collected, they can be mixed together in a special chemical mixer. The mixture takes about five to seven minutes to make and thirty seconds to one minute to duplicate.


"AT1521" was developed by the research team operating from within Umbrella's official Raccoon City facility. Linda and Carter, surviving developers of the vaccine returned to the facility on October 1, 1998 to retrieve it in hopes of widespread production of the vaccine.[18]

The exact details of the serum itself are unknown due to the short role it played in the storyline (the sample being destroyed by the rampaging Tyrant R not long after its initial appearance). However, Linda did remember the reagent's base, and thus was able to remake a sample.


The fourth is an anti-"t" agent known as the t-vaccine created by WilPharma Corporation. Unfortunately, most of the samples were destroyed by Frederic Downing right after the Harvardville Airport t-Virus outbreak, and the last t-vaccine sample was taken by Downing so that he could sell it to bioterrorist general Miguel Grandé along with the t- and G-virus samples, but he was caught by Claire Redfield and Leon S. Kennedy before he could sell it.[19] It is possible that the US Government used this last anti-virus sample to produce more in case of future outbreaks.


There are also some prototype antibodies for the t-Virus used by the UBCS. They were only mentioned by in a pocketbook kept by a deceased UBCS mercenary in the St. Michael Clock Tower.[20] It should be noted that no "zombified" UBCS members were encountered in the Clock Tower. But they also notes that the virus had already mutated and already neutralized the Antibodies effects.

Regular Anti-viral pills can slow down t-Virus mitosis temporarily.[21]

Further notes

  • As the "t" and Uroboros viruses are variants of Progenitor, it can be deduced that for someone to co-exist with either of the three viruses, they must have specific genes that vary between them. This trait is incredibly rare, and that only 30 people statistically have it in the United States - with a population of 300,000,000. This 1 in 10 million chance of having this trait means that Tyrant development is kept short of suitable candidates. This was the reason why Umbrella sought to clone Sergei, a carrier of this gene.
  • In the video games, the t-Virus is green in colour, but is blue in the films, while the green canisters are speculated to be the antidote.
  • In Resident Evil Zero and Resident Evil Survivor the t-Virus (along with its parent virus in Resident Evil 5) is visible under microscope. It should be noted that virions are generally not large enough for the naked eye to see with a standard light microscope, though some viruses are known to be larger than certain bacteria species.
  • In Resident Evil 2, the color of the T-virus is green while in Operation Raccoon City, the color of the virus is blue.
    • In the first film of Resident Evil, the color of the T-virus is cyan instead of green but in a zig-zag design and the latter antivirus is lime green.
  • According to Luis Sera, a t-Virus sample was being held at the Madrid Police Department in 2004.
  • Several viruses created later were based on the t-virus, including the G-Virus, T-Veronica virus, Uroboros virus, T-Phobos Virus and the C-Virus which was a combination of an enhanced veronica virus and the G-virus.



  1. Capcom. Resident Evil (1996). Scene: Wesker's betrayal (Chris). No, the worst happened with the tyrant virus.
  2. Resident Evil 5 (2009), ??
  3. 3.0 3.1 Resident Evil 5 (2009), file: "History of RESIDENT EVIL"
  4. 4.0 4.1 Resident Evil 2 - Annette Birkin refers to William as "The man who created the t-Virus"
  5. Resident Evil 0 - William walks to a dying Marcus and tells him he will "take over" his research
  6. 6.0 6.1 Wesker's Report II (Part 4: Enter Nemesis)
  7. Capcom. Resident Evil. (Capcom Co., Ltd.). File: Keeper's Diary.
  8. Resident Evil Survivor (2000), file: "How to extract Beta Hetero Nonserotonin"
  9. Capcom. Resident Evil: Dead Aim. (Capcom Co., Ltd.). File: Emergency FAX from Paris Branch.
  10. Capcom. Resident Evil: Dead Aim. (Capcom Co., Ltd.). File: Reconstructuring Notice.
  11. 11.0 11.1 11.2 11.3 Resident Evil Zero (2003), file: "Marcus' Diary 1"
  12. Resident Evil Zero (2003), file: "Leech Growth Records"
  13. Resident Evil Zero (2009), scene: "Confrontation With Marcus"
  14. Wikipedia: Viral Replication at Wikipedia
  15. Resident Evil 3: Nemesis
  16. Resident Evil 3: Nemesis (1999), scene: "Hospital Scene"
  17. Resident Evil Outbreak
  18. Resident Evil Outbreak File 2, "end of the road"
  19. Resident Evil: Degeneration
  20. Resident Evil 3: Nemesis (1999), file: "Merc's Pocketbook"
  21. Resident Evil Outbreak (2003), item: "Anti-Virus (L)"

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