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The T-Virus in it's vial

The t-virus (short for Tyrant Virus) was the breakthrough for Umbrella Pharmaceutical in viral weaponry spawned from an attempt to weaponize the Progenitor virus for military use and application. A highly adaptable mutagenic toxin, the t-virus would prove to be the basis for the majority of Umbrella's research. The very first strain of the t-virus was created by Dr. James Marcus. Research was then carried out on the virus simultaneously by Albert Wesker and William Birkin and progress excelled at the Arklay Research Facility. To date, there are now countless variations and strains of the virus.


t-Virus Project

On September 19, 1977 during his research into leeches, Marcus had discovered a method of creating a new, more powerful virus using the Progenitor virus as the base element and mixing it with leech DNA. The result was the t-virus, a weaponised variant of Progenitor. The virus was completed on January 13, 1978. Shortly after, Marcus conducted experiments on several animal species including monkeys, insects and frogs (eventually leading to the development of the Eliminator, Lurker and Plague Crawler). While definite results were observed, Marcus ended the experiments furiously after not getting the results he desired, with the belief that humans were the only viable test subjects. In the time that followed, many unwilling human test subjects were victims of Marcus' experiments - including several junior executive candidates at the Training Facility, with the total count being around 20. Soon after his discovery, Ozwell E. Spencer, another founder of Umbrella who Marcus had recently come into bitter terms with, ordered a set few Umbrella employees to retrieve a sample of the virus from Marcus. However, they were unsuccessful, instead becoming specimens for Marcus' research.

This was remedied by Spencer's use of Albert Wesker and William Birkin, top students at the Training Facility who both Spencer and Marcus fiercely trusted. The two successfully managed to retrieve a sample of the virus soon after its completion by Marcus, allowing the Arklay Research Facility. Here, the t-Virus Project began in earnest.

First Phase

At the top-secret Arklay Laboratory, Wesker and Birkin became chief researchers in charge of R&D into the t-virus and B.O.W. research. What became known as the "First Phase" of t-virus development following its initial completion was an effort to stabilise the virus well enough to produce viable bio-organic weapons. In total, it took 3 years for such a result to be realized.

Second Phase

In 1981, the virus finally became stable enough to produce a Living Biological Weapon in the form of the "Zombie" creature and the project reached its Second Phase.

Due to compatibility issues between the virus and the human genome, it became clear that the virus would only infect 90% of a population with the remaining 10% making a lucky escape from the virus' effects. Unhappy with this development, Spencer ordered for a 100% infection rate. Meanwhile, Birkin engineered a biological weapon with an increased emphasis on fighting ability by mutating human genes with the t-virus and additionally combining the genetic material with another creature, producing a creature capable of killing all human beings in a designated target zone. This B.O.W. was officially dubbed "Hunter".

In 1983, Wesker began to ponder about the adaptability of the t-virus and the risk of secondary infection, due to it being able to infect and mutate the genomes of both animal and plants alike. Among the research conducted during the Second Phase, other B.O.W.s were produced from other creatures. These included the "Cerberus", based on military trained dobermen. "Neptune", based on Great White Sharks. "Web Spinner", the premier development of viral research on arachnids, based on spiders. The final result of the facility's experiments was the "Chimera", developed like the Hunter by mutating the human genome with the t-virus and combining the genetic material of a fly. A rumoured 5th B.O.W. was also produced, known as the "Tick", an insect-based subspecies related to the Hunter and Chimera.

In 1988, as the project was about to enter its Third Phase, certain figures within Umbrella called for the research of James Marcus to be shut down. Under top-secret special orders from Spencer himself, Wesker and Birkin assassinated Marcus and stole his research for use in their own project. As a research team conducted an investigation on the B.O.W.s produced by Marcus, they deduced that humans were the most viable test subjects for the virus. In response, the Arklay B.O.W. Research Team commenced the Tyrant Plan under Birkin's direction.

Third Phase

The Third Phase of the t-virus project began in full with the Tyrant Plan-- the goal to produce the ultimate B.O.W.. The B.O.W. in question was a highly sophisticated fighting biological weapon capable of receiving and understanding orders and carrying them out with utmost efficiency-- dubbed "Tyrant" after the project and the virus itself. Unlike previous experiments, the Tyrant would not be an animal, but a human subject. The idea was to administer the maximum amount of t-virus to a human subject and adapt it fully to the host. However, a huge problem lay with the fact that only a set few people had the ability to become a Tyrant. As well as this, the strain of the t-virus used to create Zombies and Hunters was deemed unsuitable due to its tendency to destroy the subject's brain cells, limiting intelligence, which was required to successfully develop a Tyrant. In order to correct this issue, Birkin worked to extract and develop a t-virus variant which would cause the least amount of damage to the brain. However, the Genetic Analytic team at the Arklay Research Facility turned up another issue, only 1 in 10 million people would possess a genetic compatibility to the new variant.

With the project at a standstill, Wesker instead set his sights on the parasite developed by the Sixth Research Facility in France. After administering the parasite to Lisa Trevor, they observed the genesis of the G-virus and in response, both Wesker and Birkin left the Arklay B.O.W. Research Team in 1991 for their own reasons. Not long after however in August 1991, one Sergei Vladimir approached Umbrella. After passing the test for becoming a Tyrant, Sergei was convinced by Nicholai Zinoviev to turn over 10 clones of himself to Umbrella. Sergei did so in the end, and the Tyrant Plan and the t-virus project in general resumed.

With compatible specimens at the ready, the Arklay Research Facility produced two Tyrants-- the failed Proto Tyrant (T-001 Type) and the successful Tyrant (T-002 Type) which was named after the project. T-001 was a success in theory, it presented all of the characteristics of a successful B.O.W, however the lack of further development into controlling the mutative and erosive nature of the T-virus meant that it was far from perfect. The T-002 was aimed at rectifying this issue. The T-002, unlike the T-001, was kept in development for a longer time to make further improvements, and was nurtured so as to reach its full potential. The T-002 was a vast improvement over the T-001, stronger, refined and able to be controlled and follow simple orders. Meanwhile, another Tyrant model was developed in the Raccoon City Underground Laboratory run by Birkin. This model, the "Tyrant T-103 Type" was superior to the previous two, but required the data of the T-002 to be completed. After a successful experiment with the T-002, the Arklay B.O.W. Research Team also commenced the "Talos Project"-- producing the T-A.L.O.S. prototype.

Over the years, t-virus R&D was continued by Umbrella, who refused to abort the project until its dismantlement in 2003.


By 2003, the last remnants of Umbrella were finally dismantled and research on the t-virus by Umbrella was brought to an end. Taking no chances after Raccoon City, the United States government authorised research on the t-virus in the hopes of creating a vaccine that could be distributed to the public. WilPharma, a pharmaceuticals firm, was tasked with this responsibility and as such set about researching samples of the t-virus. Unfortunately, part of this research involved the experimentation of the t-virus in India.

Following Umbrella's dissolution, countless strains of the t-virus wound up on the black market, likely perpetuated by former Umbrella employees, leading to a new age of bioterrorism. Due to this, the B.S.A.A. (Bioterrorism Security Assessment Alliance) was founded under the jurisdiction of the United Nations, with one it's it's founding members being Chris Redfield. With the creation of a 100% effective vaccine by WilPharma and its retrieval by the U.S. government, it is assumed that the t-virus is no longer a threat to developed nations.


The t-virus is the only known Umbrella-made virus that possesses the ability to infect almost all known animal and plant species. Whether this attribute is an inherited trait from the Progenitor virus is unknown at this time. It is also known to go through rampant and sudden mutations on its own, depending on its environment, thus leading to the redundancy of many of Umbrella's own developed viral anti-bodies. The virus' traits based on each section of the animal kingdom is detailed below.


Seconadary infection of a mammal normally leads to:

・ rotting of the skin, congestion

・ deterioration of muscle fiber

・ extreme degeneration of intelligence

・ paralysis of pain sensations

・ metabolic activation

・ heightened aggression

These physical traits can be found in almost all t-virus mammals, namely Zombies, Cerberus, Bats and Eliminators. The extreme degeneration of intelligence is also dependant on species, as Eliminators are known to possess much more intelligence than zombies and are capable of understanding orders. In humans, t-virus infection is only 90% effective, with the remaining 10% of the population having a natural immunity to the virus, even when directly bitten by a Zombie. As well as this, the rate of the infection is unique to each person, and can be influenced by several factors which may speed up or slow down infection.


In arthropods, the most common trait is an increase in size which occurs almost indefinitely regardless of the species involved. The exact size varies, with the "Large Roach" having the smallest size increase. Fleas, wasps, bees, spiders, scorpions, worms, centipedes and moths have all been known to undergo extremely dramatic size increases. Along with this trait, heightened aggression, metabolic activation and a change in diet are all common.


Like arthropods, reptilians undergo the same size and aggression increases. They do not normally appear to have any physical degradation due to their scales.


Although very few cases of amphibian t-virus infection has been observed, they have been known to experience the same size increase, change of diet, metabolic activation and heightened aggression as others. Their unique skin makes them appear "normal" in comparison to other creatures which have exposed flesh.


Plants, once infected with the t-virus generally gain some form of sentience and, depending on species, increase in size. Some have also been known to gain poisonous attributes. The first recorded t-virus infected plant with such an ability was the Plant 42 within the guardhouse of the Arklay Research Facility. Other examples include the "Monster Plant" and "Evil Shade".


While birds (such as the Crow, or Hornbill) do not undergo an increase in size, they become extremely aggressive and their diet changes to include meat to make up for their metabolic activation. On top of this, while they do undergo physical degradation, their feathers make them appear "normal".

t-Virus Versions

Over the years, many different strains and variants of the t-virus were produced by Umbrella throughout its many facilities, with many being completely unrelated to each other. Below is a list of known examples.


Marcus ver.

The first strain developed by Marcus from the Progenitor virus after combining Progenitor with the genetic material of leeches. It is the strain upon which all others are based.

Stabilized ver.

Developed in 1981 at the Arklay Research Facility, until the development of this improved strain, it was almost impossible for the Arklay research team to develop B.O.W.s, even Zombies. This variant is the version ideal for creating zombies and Hunters and other creatures.

Crimson Head ver.

A variant produced within the body of the Crimson Head Prototype 1, it was cultured by Umbrella and is the strain responsible for the outbreak in the Arklay Research Facility. It was also leaked at some point in the Management Training Facility. It is known for its unique process known as "V-ACT" which can revive an incapacitated zombie in a deadlier state. Aside from the V-ACT process, it is not much different from the stabilized version.

Birkin ver.

The strain known widely as the cause of the Raccoon City outbreak. Unlike the Crimson Head version, it does not produce Crimson Heads at all. Instead, it produces a new life-form known as the "Licker" with a process similar to V-ACT. It is based on the stabilized variant, but has been enhanced further.

Tyrant ver.

The variant extracted and developed by Birkin in order to cause the lowest level of destruction to a subjects brain cells, thus keeping intelligence. However, this variant is only compatible with 1 in 10 million people, and only one man to date has been known to have this said genetic match-- Sergei Vladimir.

Rockfort ver.

An experimental, enhanced airborne version of the t-virus developed on Rockfort Island.

Artificial V-ACT ver.

Developed by Umbrella based on the cultured Crimson Head version, this variant is known for its unique ability to induce a forced V-ACT process upon injection. Although the resulting zombies are not full Crimson Heads, they are faster and stronger than normal zombies.

Progressive Tyrant ver.

The final product of the "Tyrant Plan" capable of producing a Tyrant without any degeneration in intelligence. It was used by Sergei Vladimir on himself on February 18, 2003.


A variant strain of the t-virus which was supplied to the private hospital in Raccoon Forest by Umbrella's front company "Drugs Inc." in 1993 and administered to two patients, Doug Frost and Dorothy Lester. Unlike the normal version of the virus, this variant was recorded to actually destroy cancerous cells and briefly restore health before eventually reverting to the virus' normal behaviour, turning both Doug and Dorothy into Zombies.


There were three known vaccines to the t-virus that were developed in 1998, before and during the outbreak in Raccoon City. A perfect vaccine was later created in 2005. Anti-bodies were a product of Umbrella's own anti-viral research, but were generally either completely ineffective or only slightly effective due to the nature of the virus to mutate randomly depending on its environment.

t-Vaccine (Raccoon General Hospital)

The first was developed by Douglas Rover of the Umbrella Medical Service, which was developed in very small quantities but not enough to help stem the outbreak. This particular vaccine was later synthesised by Carlos Oliveria in an effort to cure Jill Valentine, who had been infected by the Nemesis-T Type. It is unknown if the vaccine was completely effective, as the T-virus within Jill was not destroyed, but merely put into a dormant state. Due to the lack of further samples of the vaccine, this cannot be ascertained.

Daylight (Raccoon University)

The second was the brainchild of Greg Mueller and Peter Jenkins, and was codenamed "Daylight". Developed at Raccoon University by the pair, it was a unique reagent that could suppress the growth of the t-virus. Daylight was comprised of the following components - P-Base, which acted as the base for the vaccine. V-Poison, derived from wasp venom as a culture catalyst, and finally T-Blood - essentially blood taken from a creature infected with the t-virus. However, the project was not entirely a valiant effort, as Greg Mueller had selfishly aimed to use the vaccine to destroy Umbrella, believing that a vaccine against their most valued viral agent would severely cripple the organisation. Unfortunately, no samples of the reagent were retrieved from Raccoon University, which was destroyed by Nicholai Zinoviev.

AT1521 (Umbrella)

The final vaccine was developed at the laboratory in Raccoon City, primarily by Michael Jenkins. It was Umbrella's only official attempt at synthesising a vaccine for the t-virus. Despite this, it was only effective on those who did not show any symptoms. It does not eliminate the virus and instead inhibits the virus' growth rate and slows it down. It was tested on lab mice with a 99.91% success rate. The only known sample was destroyed by the Tyrant 0400TP, however, additional samples may have been cultivated by former Umbrella researcher Linda, who knew how to re-create it. 1

t-Vaccine (WilPharma)

Developed by WilPharma. Following the Raccoon City Incident, extensive government sponsored research was carried out in the hopes of finding a vaccine. WilPharma was a key pharmaceutical company that worked on such a vaccine. To achieve their goals, WilPharma conducted human experimentation on test subjects in India with the resulting findings being used in the development and synthesis of a vaccine. In 2005, the vaccine had a successful trial run following a terrorist incident in India and soon after, samples of this vaccine were distributed to Harvardville Airport in response to an outbreak. All of the U.S. Marines involved in the clean-up operation were injected with the vaccine, who proved its success when they reclaimed the entire airport without any infections. All of the trucks carrying the vaccine were destroyed, but the last remaining sample was recovered from Frederic Downing by Leon S. Kennedy.

Anti-Bodies (Umbrella)

As well as vaccines, Umbrella made several attempts at creating viable anti-bodies to fight off infection. While some of these anti-bodies provided some results at slowing down the infection rate, their overall effectiveness was quashed due to the virus' mutative nature, rendering them virtually useless after a set period of time. Anti-bodies were administered to the many U.B.C.S. troops deployed during the Raccoon City Incident. t-virus anti-bodies actually find use in the manufacture of other viral agents such as the t+G-virus and Uroboros virus.

Umbrella did however develop stronger, better quality anti-bodies. Whilst not 100% effective, they had a much higher defense than the ones administered to normal U.B.C.S. members. These anti-bodies were administered to the Supervisors among the U.B.C.S. 2

Anti-Bodies (Jill)

Due to the vaccine administered to Jill Valentine and her subsequent stasis in 2006, it was found that the vaccine actually did not immediately destroy the virus, instead putting it into a dormant state. When the virus reactivated, it soon disappeared due to an abundant amount of powerful anti-bodies within her body. These anti-bodies rendered her completely immune to the virus and allowed Albert Wesker to correct the potent nature of the Uroboros virus.