A virus is classed a pathogen which can infect the cells of all forms of organic life, and the ultimate goal is to replicate itself inside of it's host and spread to others via transmission. It can be contracted by many different ways, whether it be direct transmission by saliva in animals, by injection into the bloodstream, picked up through the air, absorbed, or by ingesting.
The t-Virus (Tyrant Virus) is based on the Progenitor virus which was first discovered in the flowers of a plant named Stairway of the Sun in West Africa. An ancient tribe named the Ndipaya ritualistically ate the flowers and became infected - most would succumb to the virus and die, but very rarely there would be a survivor and be transformed with superhuman strength, agility and increased intelligence.
Umbrella eventually learned of this in the 1960's, and sent teams to cultivate the flowers for themselves, extract the Progenitor virus, successfully re-recreate it in lab conditions - and perform research on it until eventually they engineered the t-Virus, with the hope that eventually they could perfect it and create numerous superhuman soldiers as well as create specific Bio-Organic Weapons (B.O.W.s). Their test subject were typically infected by an injection of the virus paired with enzymes and different kinds of solution to improve the results. Then the test subject would be monitored and either continued to be tested, or destroyed.
t-Virus research began in the Arklay Laboratory which was hidden underneath the Spencer Mansion
in the United States. The initial test subjects were George Trevor, Lisa Trevor
and Jessica Trevor - only Lisa survived the continuous infection and testing. Lisa would later be found by S.T.A.R.S., alive, but horribly mutated.
Dr James Marcus
, one of the founders of Umbrella, was part of the team that discovered and gave a name to the Progenitor virus and began using leeches in his research - first injecting them with the virus, and then after a time the virus mutated inside their bodies, thus producing what is now known as the t-Virus, which was then extracted. It was named the t-Virus to set itself apart from the Progenitor virus, and also because of it's ability to create superhuman soldiers named Tyrant.
Initial testing with the virus saw different results than with the Progenitor virus. It did not kill the infected as before, it turned them into zombies - i.e. - personality and intelligence is all but lost, tissue begins to die and aggression increases massively. On the positive side, the infected have increased durability, which meant in large groups they had the potential to infect everything around them with the virus - which is exactly what happened wherever there had been an outbreak.
Four strains were developed in the Arklay Laboratory:
1. Alpha (α) - This strain was developed to test the effects of the virus on animals. One of the first was a great white shark which the research team named Neptune
. Umbrella considered this strain a disappointment as it did not change the genetic makeup of the shark enough, with only minor mutation and changes of strength. They also developed a Spider
named Webspinner - with this the Spider
increased in size massively to Umbrellas surprise, they continued to survive. Complex physiological changes had to have occurred inside the body for their surface-to-volume ratio to be large enough for them to continue to breathe.
2. Beta (β) - This strain was developed specifically for dogs and wolves. This is the virus strain which created the Cerberus
, which were the dogs which chased S.T.A.R.S. teams into the Spencer Mansion
. This was also considered a failure by Umbrella, despite the fact that in theory the Cerberus
could be trained as long as they had constant direction and supervision, and a steady supply of food. However, it's likely the brain damage was still to great for this to be viable in the long run.
3. Beta-2 (β-II) - An upgraded version of Beta, this was used in the creation of Hunters, which were created by splicing human DNA and lizard DNA, and using the Beta-2 strain as a bonding agent. The resulting creature, named the Hunter was then cloned to ensure that all were identical. This was by far the most successful result at this time. The Hunter Project was deemed one of Umbrellas greatest successes, and as such the clones were used in many different future projects.
4. Epsilon (ε) - For a long time Umbrella were attempting to use the Beta-2 strain to create superhuman soldiers, but the strain was causing far too much brain damage to it's subjects. Thus, Epsilon was developed. This virus is far and away the most common form of t-Virus - it is the strain which created the Tyrant from the Mansion incident, and it is also the same strain which was released throughout the mansion and mutated all of the infected into zombies. Most zombies encountered in the early Resident Evil series (1-3) are Epsilon-strain infected. This includes further mutated creatures such as Lickers and Crimson Heads.
After the Mansion incident, and the further outbreaks of Raccoon City and later Rockfort Island, other viruses were developed using the t-Virus as a base such as the G
-Virus (Golgotha), developed by Dr William Birkin
and eventually led to his transformation into a monster and subsequent death. Before his death, Dr Birkin developed a virus simply named Prototype and injected his colleague Dr Albert Wesker
with it as he appeared to fit the genetic profile - and he gains superhuman strength, intelligence and speed. The giveaway that Dr Wesker was infected was his cat-like glowing eyes - Dr Wesker tended to wear sunglasses at all times which helped hide this trait.
Due to the promising results of the virus, there have been many many other viruses based on the t-Virus in the Resident Evil universe, such as t-Veronica, t-Abyss and t-Phobos.
Infections derived from the t-Virus are also used in the creation of more specialised B.O.W.s, such as the various Tyrants, including Mr X and Nemesis. Almost all of these used the t-Virus with a combination of a new type of virus or parasite in order to test their effectiveness.
There have also been attempts to create a cure for the t-Virus. Umbrella themselves created antiviral agents, but as the t-Virus is so unstable and mutates quickly, it was not a permanent solution.
In Resident Evil 3, there is a vaccine available which can be synthesised - and is used to cure Jill Valentine
from an early infection by Nemesis. It is unlikely the vaccine would work if the t-Virus had chance to fully infect the body. The vaccine appeared to almost fully destroy the virus, although some cells would go into a dormant state similar to the V-ACT process. Her body now had the ability to create antibodies in her blood, which were later used for continued research into Progenitor-based viruses, such as Uroboros