The basis of T-Veronica's research came with the discovery of a retrovirus existing within the genome of some ant queens. Alexia mistook the socialist nature of an ant colony for one with complete adoration for their "queen", and likened it to her own megalomaniacal lifestyle and personality. She then began considering the possibility of merging the genome of this virus with that of the Progenitor virus. Plant genes were also added into the virus' makeup.
The first step in human testing came in 1982, when Alexia and Alfred infected their "father", Alexander Ashford, with the virus. For whatever reason, he failed as an adequate experiment; he was imprisoned within the Antarctic Base, terrifying the facility's workers with his inhuman growls, earning him the name "Nosferatu".Soon after her father's degenerative mutation, she christened the virus "T-Veronica", in name of her cell-donor.
It was soon after this that Alexia decided to experiment on herself. In order to prevent the degeneration Alexander faced, Alexia concluded that going into a cryogenic coma for some fifteen years should allow her to adapt to the virus.
At one point in this year, Albert Wesker intercepted a rumour regarding the existence of this virus. Expecting it to be somewhere in Alfred's Rockfort Island base, he and the Hive/Host Capture Force attacked the island, leading to a biological outbreak of the T-Virus. Eventually, it was discovered by Wesker that Alexia was in fact alive at the Antarctic Base; he concluded, rightly, that he would find the virus there. He left via a submarine on his way to the base, situated in the Ross Ice Shelf.
Shortly after Alexia's revival, she proceeded to experiment on Steve Burnside. While he didn't have the benefit of a fifteen-year period of hibernation, Steve managed to counter the virus not long into his mutations, as he regained his sanity - unlike Alexander, the virus had not killed off his brain cells; he died soon after when a psychically-controlled tentacle smashed him against a wall. Later on, Alexia used the strain of the virus in her body to mutate into a powerful being during her battle against Wesker.
Alexia herself mutated further into a queen ant monster and was killed by Chris Redfield with the experimental "Linear Launcher". With nothing surviving the ensuing destabilisation and explosion of her body, the capture force instead took Steve's body for experimentation.
In order to impress Derek C. Simmons, Carla Radames acquired a sample of the T-Veronica virus and began experimenting with it in hopes of making a "perfect virus", despite her first thought that T-Veronica was an "obsolescent". By removing the genetic code of the virus which created sudden mutations and combining it with parts of the Progenitor virus, Carla developed a new variant of the T-Veronica virus: "T-02".
Unlike T-Veronica, T-02 did not degenerate its hosts' mental faculties, removing the need for lengthy incubation periods (as with Alexia) or constant organ transplants (as Javier Hidalgo would do for his daughter Manuela) to keep the virus stable. This greatly increased the potency of the virus, as well as its viability as a bio-weapon.
Carla later combined T-02 with the G-Virus variant found in Sherry Birkin's body. The resulting pathogen - the C-Virus - combined the greatest elements of T-Veronica and G, transforming its victims into intelligent, extremely dangerous creatures.
Some years later, South American drug lord Javier Hidalgo ceased purchasing B.O.W.s from the Umbrella Corporation, who had desperately begun to inflate their bio-weapons prices due to the Raccoon Trials. The T-Virus variant he had infected his wife, Hilda, with to treat her illness had begun to backfire. It was at this point that Wesker began doing business with him, selling him samples of T-Veronica at a much more reasonable price. The virus, when given to Hilda, unfortunately transformed her into a grotesque aquatic creature.
However, Javier's faith in the virus had not diminished; when his daughter, Manuela, became ill, he injected the virus into her while searching for ways to prevent the same degeneration that had taken Hilda. Javier later came to the conclusion that a means of countering the virus' control over the body was to constantly replace the infected tissue until the body was able to safely assimilate the virus. Thus, Javier arranged for Manuela to undergo a series of organ transplants for the next fifteen years - this way, she would remain in control of her body and continue to live a normal life with her father. To facilitate this grand plan, Javier's crime syndicate, the Sacred Snakes, began kidnapping young women of Manuela's age to be used in forced organ donation.
When US Government agent Leon S. Kennedy and USSOCOM member Jack Krauser began investigating the region in search for the Umbrella researcher who had been selling bio-weapons to Javier, they discovered Manuela. Being led to Javier's mansion, they discovered the organ donors and Hilda. Soon after, Javier infected himself with the virus by merging with the V-Complex in order to kill Leon and Krauser. His consciousness soon faded and the horrific creature took over; it would no longer resist trying to kill her. It was at this point that Manuela also realized the psychological aspect of T-Veronica: if she gave in, she would no longer feel pain; if she resisted, she would die human. She chose to die human in order to save Leon, throwing her combustible blood at Javier until he eventually died. Although weakened from blood loss, she nonetheless survived as an ordinary human.
The T-Veronica virus was not distributed on a wide scale like other viruses and parasites in the series, but it appears to operate similarly to its predecessors, the Progenitor Virus and the T-Virus. Notable differences include a tendency for infected individuals to manifest arthropodic traits in their mutations, such as hard carapaces or insectoid limbs. The blood of a T-Veronica host often changes into a chemical that spontaneously combusts on contact with oxygen, allowing the host to weaponize their own blood as a projectile.
Like the T-Virus, the T-Veronica virus has a tendency to cause severe mental degradation in its hosts. Unlike the T-Virus, successful fusion with the T-Veronica virus does not require the presence of certain genes or hormones in its host - instead, the stabilizing factor appears to be the rate at which the virus is allowed to spread within the body. In order to perfectly co-exist with the T-Veronica virus, the host must live with it for a number of years, allowing the virus to adapt to their body. Alexia Ashford achieved this by entering a state of cryogenic stasis, causing the virus' infection rate to slow to a crawl, while Javier Hidalgo planned to regularly replace Manuela's infected organs with fresh transplants (thereby retarding the virus' spread by forcing it to constantly "re-infect" her organs). If this is not done, the T-Veronica virus will produce a similar result to the T-Virus, mutating the host into a mindless zombie whose singular desire is to consume flesh and infect others. However, Leon noted there was something different about the zombies produced by this virus compared to the T-virus. As with many variants of the Progenitor virus, the mutations induced by the T-Veronica virus are largely dependent on the mindset of its host.
Notably, two people infected by T-Veronica (Manuela and Steve) have been able to counter their mutations and regain control of their bodies through willpower alone. A more subtle example was Manuela's mother, Hilda, who regained some part of her humanity at the sight of Manuela and was kept at peace when she sang a lullaby that Hilda sang to her as a child. Unfortunately, when Manuela was too weak to sing the song, the monstrous personality regained control. Javier, like Alexia, was also able to control himself when mutated by the virus; however, he allowed it to take control, eventually defeating the human mind and assuming complete control as an uncontrollable beast. By the time Javier regained control over himself, he was only able to beg Leon and Krauser to kill him.
According to the V-Complex's archive entry in the Darkside Chronicles, the virus' activeness was also dependent on the outside temperature. The frigid temperatures of the Antarctic meant that the virus could not travel as easily, and the virus could not infect its surroundings as easily. The tropical and humid climate of South America, however, caused the virus to reach ginormous proportions, potentially threatening entire ecosystems.
The following is a list of subjects that were infected with T-Veronica.
- Alexander Ashford (Nosferatu) - Former head of the Ashford family and member of Umbrella's board of directors. His daughter Alexia used him as the first T-Veronica test subject, but the virus transformed him into a mindless monster.
- Alexia Ashford - A child prodigy in viral engineering, Alexia created T-Veronica and infected herself with it, having herself placed into cryogenic suspension for fifteen years. When she emerged in 1998, the virus had completely adapted to her body, allowing her to transform into a powerful mutant form and retain her mental faculties.
- Steve Burnside - A young man who was imprisoned on Rockfort Island before escaping with Claire Redfield. They were diverted to the Umbrella Antarctic facility where they were both captured and Alexia injected Steve with T-Veronica. In his mutated state, Steve attacked Claire, but his own personality reasserted itself and he resisted Alexia's control. Alexia then killed Steve using a plant-like tendril.
- Hilda Hidalgo - Wife of South American drug lord Javier Hidalgo. Afflicted with a degenerative disease, Javier injected Hilda with T-Veronica in an attempt to save her, but caused her to transform into a monster.
- Manuela Hidalgo - Daughter of Javier and Hilda. Stricken with the same disease as her mother, Manuela was also injected with T-Veronica. To prevent her from mutating, Javier began abducting young women to harvest their organs, transplanting them into Manuela to delay the virus' progress. This procedure worked and Manuela retained her humanity.
- Javier Hidalgo - Head of the Sacred Snakes crime syndicate. In order to stop Leon and Krauser from taking Manuela from him, he injected himself with T-Veronica and merged with the mutant V-Complex plant. The virus soon overwhelmed his personality, and in his last moment of sanity, begged Leon to kill him.