Forced Evolutionary Virus



FEV (Forced Evolutionary Virus) is an artificial virus created by West Tek's NBC Division. Its ability to force changes in both the genotype and phenotype made it one of the most important mutagens in the wasteland, harnessed by different organizations and individuals for their own purposes both before and after the Great War.

Overview
The strain responsible for creating the Mariposa super mutants is called FEV-II and represents the pinnacle of pre-War research into the virus. A different, unfinished FEV strain is the source of the super mutants infesting the Capital Wasteland, intellectually inferior to their West Coast cousins. Other strains created the monsters of Appalachia and the distinct super mutants of the Commonwealth, as well as served as the basis for the Institute's third-generation synths.

The FEV exists in various forms across all of the Fallout games, mainly to serve the goals of the various antagonists. It was through the FEV that the Master made his race of super mutants and how the Enclave meant to purify the world of mutation.

Virology
FEV is a megavirus, with a protein sheath reinforced by ionized hydrogen. It is capable of absorbing neutrons without becoming radioactive (i.e., it cannot be sterilized by radiation). In terms of functionality, FEV is a shifting-absorptive virus, copying DNA patterns and storing these patterns in exons much like a retrovirus. These exons, combined with the FEV, are re-injected into the host cells in typical viral infectious fashion. This causes the host cells to "regenerate" their DNA with FEV's corrections that eradicated recessive genes.

FEV comes pre-loaded with introns of corrected DNA that eradicate recessive genes responsible for ailments and alters RNA strands for greater transmission of signals. DNA altered by the virus renders the subject immune to biochemical weapons, radiation, and common diseases. Cellular division rate is increased, with mitosis occurring at 115% of the normal human rate. Normally non-regenerating tissue, such as neural tissue and non-somatic cells, also begin to replicate, allowing for real-time regeneration.

A peculiar feature of FEV is that it is highly corrosive and volatile in its pure form, capable of degrading rubber containment seals like acid, though without any acidic residue. This also rendered attempts at creating an effective decontamination process difficult, as FEV could render most compounds inert before they could neutralize the virus. Eventually, combining a booster with an antiviral compound created a neutralizing agent capable of rendering FEV inert when applied in sufficient quantities.

Variation in mutation
A notable feature of FEV is that it partially relies upon the DNA of the individual coming in contact with it. Coupled with portions of its own recursive code, effects of exposure can be unpredictable, particularly when non-humans are exposed to the virus, or multiple organisms are placed into the same vat (vide centaurs).Fallout Bible 0: "3. Are the radscorpions a product of the FEV virus? When you talk to the doctor, Razlo, in Shady Sands, he tells you that they were once American Emperor Scorpions but that he has no idea how they mutated because radiation alone couldn't have done it. For that matter, what about all of the other creatures of the wasteland? Which ones have been mutated by FEV and which ones haven't? Maybe in the bestiary each creature could have a stat that shows it's level of FEV infection." "Answer: Mantises. Most species of rats. Gecko lizards. Brahmin Scorpions Ants Various varieties of plants, including the Venus Flytrap. Rumor has it some dogs were affected, but no one's seen any, so for now that's just rumor. Of course, the centaurs are a mash of human, dog, and various other parts... but hey, who knows how that mutation came about. Grey was probably messing around in one of his labs.
 * The radscorpions are a result of a combination of radiation and the FEV virus, and Razlo in Shady Sands is correct - they were originally Emperor Scorpions that have grown... big.
 * FEV-Infected Critters in the wasteland include almost all the ones you've seen in F1 and F2:
 * Creatures not mutated by FEV probably did not survive the aftermath of the Great War, with the possible exception of cockroaches... and perhaps normal ants, though there are FEV-infected versions of these species.
 * No one knows where those bird noises in Vault City came from.
 * I'll try to include a chart of FEV-infected creatures in future additions as well as other critters that you may not have seen in F1 and F2. Most likely a great majority of insects were affected (they tend to breed much faster, and their mutations tend to become evident pretty quickly as the generations advance), possibly beetles, some spiders, cockroaches, and other creatures." This feature of FEV made it incredibly versatile, though tweaking the genome of the virus required extensive experimentation: Strains would typically produce unstable results, with few viable, stable strains.

Changes to DNA are expressed phenotypically by recursive growth patterns integrated into the FEV. However, apart from the genome in the virus strain, effects also vary greatly depending on the method of exposure. Prolonged immersion in the virus creates the most stunning transformations, such as super mutants and centaurs. In Mariposa this has been achieved by a 24 hour exposure to FEV-II in the vats, achieving a severe overdose of the virus. In Vault 87, infection took place in sealed chambers, where an aerosolized virus was introduced. The exposure was relatively brief, compared to the Mariposa procedure. In Appalachia and the Institute, exposure to their own version of the virus took place in sealed tubes, where the subject was immersed for a prolonged period of time, allowing for observation of the transformation results.

On the other hand, injections of small doses of the virus will not bring about transformation but can be used to induce a variety of changes. The Master used localized FEV injections to modify himself in the early days of the Unity, and later experimented with brain injections, awakening the latent psyker potential in the subjects (though also causing permanent, terminal insanity). The Enclave used a modified FEV virus to greatly increase the intelligence of deathclaws through cranial injections (overshooting the project's goals by a wide margin).

Reverting the changes
Since FEV does not store an unaltered copy of the subject's DNA, the changes are generally impossible to revert. Theoretically, the mutation process could be reversed by infecting the subject with a secondary virus that contained a copy of the subject's original DNA and replaced the FEV's modified strands, then forced recursive growth again. However, it would also be necessary to neutralize FEV itself to prevent mutation from reoccurring. It was not possible with pre-War technology.

However, the Institute's FEV research made this possible. Dr Brian Virgil created a serum to revert the mutation. Like the FEV itself, the serum was a retrovirus, using recombinant counter-intron sequences and transcriptive exon strands together with a genetic resequencer to counteract the specific strain of FEV that Virgil was infected with. Technically, the serum did not actually revert his mutation: It restored him to a human state by recreating it using the mutated DNA as a basis. The experimental state of the serum and a buggy resequencer prevent a perfect restoration, leaving portions of the mutated code untouched. If exposed, Virgil will retain some muscle mass after the transformation and will not suffer from baldness. As the cure was also tailored to the specific strain Virgil infected himself with, generalizing the formula would take years, if not decades of additional, intense research.

Toxin strain (FEV-I)
Initial experiments into FEV were for the purpose of a biological weapon. The virulent toxin that would eventually become FEV-II saw extensive research until its much more potent quality of completely altering and mutating the human body was discovered. Research quickly swerved into heading up possibilities of a cure for New Plague and creating "super-soldiers", as well as its other applications with mutating life with the toxin. The research that was done into the biological weapon applications were filed away deep within the record vaults of Mariposa Military Base as other avenues of application saw further research and investment. On July 2236, the Enclave would uncover the records detailing the early experiments of FEV and adapt the original research into recreating FEV as a biological WMD; finally succeeding with FEV Curling-13.

Mariposa strain (FEV-II)


 In humans, phenotypical changes brought upon by the Mariposa strain are substantial, accomplished by recursive growth patterns integrated in FEV. In order for the mutation to succeed, the subject needs to have a low level of radiation-induced damageThe Vault Dweller: "How does the Virus work?" ZAX 1.2: "My research into the Forced Evolution Virus, or FEV, indicates that it is a shifting-absorptive virus. It copies DNA patterns much like RNA, storing these patterns in exons." "These exons, combined with the FEV, are re-injected into the host cells in typical viral infectious fashion. This causes the host cells to 'regenerate' their DNA." The Vault Dweller: "How do you catch FEV?" ZAX 1.2: "FEV is not 'caught', per se. It is not air-transmittable. Typically, infection is through injection, or direct physical contact with an FEV sample." The Vault Dweller: "Why isn't FEV affected by radiation?" ZAX 1.2: "The FEV is a megavirus, with a protein sheath reinforced by ionized hydrogen. It is therefore capable of absorbing neutrons without becoming radioactive." The Vault Dweller: "If the FEV re-infects the host with its assimilated viral patterns, how does it make a 'better specimen'?" ZAX 1.2: "The FEV is pre-programmed with introns of corrected DNA appropriate to the proper type of species. It therefore attempts to correct the DNA of the individual." "However, as the FEV is partially reliant upon the DNA of the individual, and also includes portions of its own recursive code, the effects can be unpredictable." "When inoculated into an individual with significant genetic damage, such as through radiation, it will cause the body's systems to suffer massive overhauling, leading to organ failure and death." "In a genetically viable individual, it re-writes portions of DNA, causing accelerated mutation, usually leading to recursive growth due to the FEV's own patterns." "This recursive growth leads to an increase in muscle and brain mass, but is often accompanied by disfigurement and damage to existing neural patterns, causing loss of memory." The Vault Dweller: "What potential long-term side effects exist?" ZAX 1.2: "As the FEV causes constant regenerative update to DNA, it would effectively render the subject largely immortal, as cell death would be offset by augmented growth." "Additionally, as the gametes of the reproductive system consist of 'half-cells' using split DNA, they could be perceived as 'damage' by FEV, which would 'repair' them, rendering the subject sterile." "However, as my laboratory facilities are damaged beyond repair, this is conjectural. I cannot offer physical proof. You will have to, in human terms, 'take my word for it.'" The Vault Dweller: "Could FEV mutation be corrected with a counter-virus?" ZAX 1.2: "No. FEV does not retain unaltered original copies of the subject's DNA. Only a virus which re-infected the subject with original DNA could reverse the effects. Additionally, there is no known way to remove the FEV itself." (ZAX 1.2's dialogue) and should not have been exposed to the mutated FEV in the wasteland. Subjects that do not meet these criteria will suffer a massive overhaul of the body's systems, leading to organ failure and extremely painful death. Fallout Bible 8: "Peter Hopkins asks: 'I was reading version 5 of the Bible, and found a bit of a conflict with current knowledge... In one of your anwers, it was said that it was random whether the FEV increased intelligence or not. However, as far as I know, FEV increases the growth and integrity of ALL cells consistently, by doubling the amount of genetic material in the cells. In this case, an increase in brain size (assuming a healthy brain to begin with) and intelligence should be regular. Another theory could be that, as the mutant's brain grows, the mass of the mutant's body increases exponentionally and the brain would not be big enough to control the whole body and sustain the throught process of a human body. Also, it is possible that while intelligence does increase initially, the brain does not gain the resistance to radiation that the body does, and the mutant develops brain damage and shows reduced intelligence. Are any of the above true? PS There is a very good report documenting the effects of FEV and how it was developed on the No Mutants Allowed message board (www.nma-fallout.com). PPS I don't know about any so called 'purists', but i am hugely interested in the fallout world and would love to FOT background in the Bible.' About FEV: ''That might be why some of the super mutants (such as the Lieutenant) are smart (or remain smart) - but generally, for some reason (I don't know off the top of my head, nor do I know if it's spelled out anywhere), they're about 30% dumber than a normal human being, if Vree's research disk in the Brotherhood of Steel is accurate. I wouldn't be surprised if the dipping process caused brain damage in dipped subjects - it's a hell of a shock to the system.'' Furthermore, everyone's favorite introspective machine intelligence, Zax, has the following to say about it:
 * When inoculated into an individual with significant genetic damage, such as through radiation, it [FEV] will cause the body's systems to suffer massive overhauling, leading to organ failure and death. In a genetically viable individual, it re-writes portions of DNA, causing accelerated mutation, usually leading to recursive growth due to the FEV's own patterns. This recursive growth leads to an increase in muscle and brain mass, but is often accompanied by disfigurement and damage to existing neural patterns, causing loss of memory.

Other possible factors that might be causing the super mutants' stupidness: - Most mutants have some degree of radiation poisoning, which may cause problems and brain damage, as mentioned above. ''- The process is unsafe - the mortality rate on "dippees" is pretty high. This is likely due to radiation poisoning.'' ''- Memory functions are "sometimes" impaired by the dipping, and intelligence loss may occur as well. Harold's memory wasn't in the best of shape after exposure.'' ''From the Pre-War experiment tapes, it looks like some mammals did display consistent increased intelligence (raccoons), while others didn't (the dogs) or even suffered brain damage (the chimps and the seizures). However, in an old Scott Campbell doc, there was a note that later subjects injected with the FEV (especially the chimps) hid their enhanced intelligence from their captors (or in the case of the raccoons, made a break for it).'' ''Furthermore, the FEV tests at West-Tek were done through injection, not dipping, so it's possible the dipping process itself that causes the brain damage. Possibly with the increased brain mass in the skull, the brain is "squeezed," and all that tasty juice runs out the ears.'' Still, on the other hand, a lot of the animals Grey talks about in his experiment tapes that were running around the Military Base were getting smarter from the FEV, and he himself became supra-intelligent. ''So there's a long-winded series of random answers. Moving on!"''

A super mutant autopsied by Vree was 3.2 meters tall and weighed 363.21 kg. The subject's muscle mass accounted for 77.41%, bone mass measured 10.23%, tissue was 9.34%, and fat mass was 3.02%. The increased muscle and body mass lead to a change in posture: FEV super mutants have a characteristic, hunched posture. The skin tone changes substantially and becomes gray with tints of light green, though as the mutant ages, it may become more green or even olive. The skin becomes much thicker and resistant to trauma, including cuts, bruises and damage from fire, acid or even gunfire. Despite this resistance to trauma, completely destroyed tissues cannot regenerate and will result in permanent scarring or organ loss.

These changes are uniform across mutants, due to the aforementioned growth patterns and pre-programmed DNA loaded into the virus. This also has the effect of removing secondary sexual characteristics, in favor of pre-programmed masculine body shape. Primary sexual characteristics, such as the penis and testicles in males and the uterus and ovaries in females are unaffected. However, super mutants are sterile, as FEV perceives gametes as damaged DNA and corrects them, resulting in sterility.

Increased size of neural transmitters and synaptic receivers in the body give super mutants acute reflexes and heightened senses. These changes are usually not accompanied by a similar rise in intellect. The FEV strain in Mariposa has a chance of modifying intelligence: while most people retain their pre-dipping intellect, a majority of the remaining group experiences a loss (typically by 30%), while the remaining minority of exceptional individuals may even experience an increase.Fallout Bible 5: "5. In F1 the Lieutenant said that the FEV raises intelligence. There are, however, very many dumb mutants. What can you say about it? And what do you think of my theory, which i've been using in my Fallout PnP campaign? Sorry, Pawel, for two things: I wasn't able to personally respond to your email because I kept getting bounced, and two, I wasn't able to comment on your FEV theory (as a reminder, I can't read fan-created material, so just send questions, comments, or facts if you can). As for the FEV enhancing intelligence, the original Pre-War FEV at West Tek did, and more consistently than the Fallout-era virus. The current Fallout-era FEV does enhance intelligence - in some people. Just not many. The Lieutenant was one of the lucky ones who didn't become a knuckle-dragging, butt-scratching moron after being dipped (and it may not have raised his intelligence, he may have been that smart before his dipping, but no records of his past exist to verify this). ''The FEV that was released out in the wasteland was mutated by radiation, so its effects changed. As for the FEV at Mariposa, the Lieutenant says the super mutants are smarter than humans ("We are highly intelligent and immune to disease"), which is only half-right, and he also says that the virus can also interfere with a person's memory, causing them to forget things. Obviously, the Lieutenant keeps forgetting that most of his super mutant forces can barely form complete sentences.'' ''Basically, the FEV in the vats only has a small chance of raising a being's intelligence (or even keeping it intact). The Master was one of the lucky ones. More often than not, it causes brain damage. It's also possible that the crude dipping procedure in Mariposa also caused imperfect mutations as well, reducing the chance of heightened intelligence.'' ''But to answer your question: the FEV at West Tek before the war caused increased intelligence in its subjects, but the FEV at Mariposa after the war rarely enhanced the intelligence of humans who were dipped. The reason for this is unknown.'' Chris Taylor says:
 * Chris Taylor: Actually, a dip in FEV has a chance of modifying Intelligence, but it doesn't always increase it. Some people do gain increased intelligence, a larger majority lose intelligence and most people remain the same. It also depends if people have enough radiation damage to be turned into ghouls or super mutants."

The loss is the result of damage caused by recursive growth and increase in brain mass, which may be accompanied by disfigurement and damage to existing neural patterns, causing loss of memory.

Vree would also theorize that super mutants are immune to common diseases and radiation and that the mutation approximate increased life expectancy by 10%. Vree was correct about common diseases and radiation, however, most super mutants can live far longer than Vree theorized. 

EEP strain (FEV derivative)


The modified, inferior FEV strain used at Vault 87 retains the recursive growth patterns characteristic to FEV, but has a different effect, which may be also linked to how infection was performed in the labs. Testing began in 2078,Fallout 3 Official Game Guide Game of the Year Edition p.42: "Super Mutants" "The Super Mutants that infest the urban ruin of Washington D.C. originated in Vault 87. Those unlucky enough to have reserved space in Vault 87 soon found themselves forcefully taken to a secure part of the vault, where they were locked in airtight chambers and exposed to a concentrated form of the F.E.V. The Overseer and his security force had no real idea what to expect; they were simply following the "plan." When the exposed vault dwellers started transforming into Super Mutants, nearly the entire vault population had been exposed. Those who hadn't yet metamorphosed knew what was coming, and, well...it didn't end well for humanity. ''The dwellers of Vault 87 were turned into Super Mutants in 2078, and have been a presence in the Capital Wasteland ever since. Most of those original Super Mutants have long since been killed. But whether it's because of the nature of the F.E.V. they were exposed to, or a simple underlying human instinct, the Super Mutants of the Capital Wasteland are obsessed with the preservation of their own species. Super Mutants are asexual and incapable of procreation, so their only way of reproducing is to kidnap other humans, drag them back to the Vault 87 chambers, and infect them with F.E.V. And so they have done, for nearly 200 years.'' ''Super Mutant society is loosely hierarchical, with the weaker (most recently transformed) Super Mutants generally giving way to the stronger. The Super Mutant hierarchy, as defined by the Capital Wasteland contingent of the Brotherhood of Steel, is as follows: Grunt, Brute, Master, and Behemoth. Generally speaking, the Super Mutants of the Capital Wasteland get bigger, stronger, and dumber as they age. The Behemoths are so strong and savage that they’re the only thing feared by the other Super Mutants."'' (Fallout 3 Official Game Guide faction profiles) where test subjects were exposed a single time to FEV in isolated chambers where the virus was deployed with an airborne aerosol. Phenotypical changes occur within three days and include increased muscle mass, changes in skeletal structure, and atrophy of sexual characteristics, both primary and secondary (including body hair). At ten days, skin pigmentation becomes a mixture of yellow and green, while its thickness and resistance to radiation and other environmental hazards rapidly increases.

However, a key problem was that the mutation did not stop. Within fourteen days of initial exposure, test subjects regress to an almost feral state, exhibiting extreme aggression at every non-mutant. While some semblance of cognition is retained, exhibited by the ability to speak, operate machines and use basic tactics in combat, super mutants of this type are typically characterized by significant mental retardation. This result is most likely brought upon by the same factor as with FEV-II: Damage to existing neural patterns caused by rapid changes in the phenotype. The effects typically cause significant damage to long term memory, again, a shared characteristic. The traumatic nature of the transformation is also a factor. The excruciating pain that accompanies it can and will cause the subjects to become insane.

Another unforeseen side effect is that the unfinished virus strain codes the body for continued growth. If a super mutant of this type eludes death for prolonged periods of time, they may become a considerable threat, reaching the size of a small building.

Institute strains


The super mutants of the Commonwealth are a completely different strain from others. While they possess the imposing musculature and resilience of the former, they have an average level of intelligence on par with examples of the latter. They are capable of following a chain of command, erecting fortifications, and even setting up traps and ambushes - such as at Trinity Tower, where Fist deliberately used Rex Goodman as bait to lure humans and weed out the weak super mutants among his host. They are also capable of speaking like normal humans, unlike their practically feral brethren from the Capital Wasteland, and consider themselves the superior race of the Commonwealth. All super mutants of the Commonwealth are products of the Institute's experiments into FEV using the abducted Commonwealth wastelanders above ground. These experiments were the base work used to progress their synths from mechanical construction to a new frontier using human DNA as a base to construct synthetic humans. The Super mutant (Fallout 4)s share a similar morphology with the super mutants derived from Appalachian West Tek's experiments on the Huntersville strain, but is unknown if the two strains are closely related.

The most advanced synthetics created by the Institute are fundamentally different from their predecessors. Despite the sequential numbering, they are unrelated to their mechanical counterparts, in fact. They are derived from Shaun's pre-War DNA extensively modified using the Institute's own research into the Forced Evolutionary Virus, combining the advantageous adaptations encoded into FEV with the versatility of the human body shape. This allowed the Institute to create a variety of synths of varying races and appearances despite the base DNA coming from only one source. They are the result of nearly five decades of research, from 2178 to 2227.

Third generation synthetics are unlike humans and some liberated synths do not consider themselves human at all. The reasons for this are multiple, chief among them is the assembly process. Other reasons include the fact that synths do not require sleep at all to function properly, are completely immune to disease, and do not require the intake of food or water to generate energy for their bodies.

Huntersville strain
The Appalachia Super Mutants were created shortly before the Great War, when the local West Tek facility contaminated the river water that ran through Huntersville with a unique strain of FEV as part of an experiment.

The super mutants of Huntersville are similar to those of Mariposa and the Institute: they have green skin, highly developed musculature, and they are smart enough to build improvised armor from waste or scrap. Although they do not use large fortifications like the Vault 87 or the Institute strain super mutants, they can occasionally build small fortresses or take entire buildings. The possess the same level of strength and durability and are intelligent enough to mount offenses against factions and other groups. Like Vault 87 and Institute super mutants, Huntersville super mutants can develop into behemoths, which can be seen guarding their main bases. The majority of the super mutants will attack the player character, but some super mutants like Grahm are friendly and will even trade with humans.

Appalachian experiments
Experiments with recombinant strains of FEV at the West Tek Research Center in Appalachia produced numerous failed mutations, with two exceptions:
 * FEVS-006443 from October 14, 2077, a Phase 2 combination strain that combined traits that resembled a number of different species. The results were considered disturbing by the scientists but provided valuable insights as to the capability of recombinant FEV. Notable changes included a number of ocular organs along the enlarged upper torso, the second set of arms ending in clawed digits, and a large sickle-shaped claw on each inner toe. The living, stable, and functioning subject was sustaining itself normally (a major accomplishment for the program) and was planned for release in Huntersville after the subsequent experiment matured. The mutant was never returned to the area until January 3, 2078, when it escaped containment and the facility. The mutant procreated, leading to the emergence of snallygaster mutants across Appalachia.
 * FEVS-006458 from October 23, 2077. Tweaking the snallygaster strain, researchers tweaked the genome, producing a giant that shattered the containment unit, but was otherwise stable (excepting the absence of a discernible head). The mutant was sedated and transported off-site, with the Great War sidetracking the convoy and allowing the Grafton monster to escape into the wild.

Albino mole rats
Before the destruction of West Tek Research Facility, lab rats were exposed to FEV. In the turmoil of the facility's destruction, they escaped into the wasteland. Similar to the Enclave's later experiments with deathclaws, these two unique rats gained intelligence and ability to talk, along with a long lifespan.

Psyker program
Apart from transforming humans into super mutants, the Master and his staff experimented with FEV by injecting it into the brains of the subjects (usually the pineal gland, but also the amygdala or medulla), triggering changes in brain chemistry. These experiments had limited success: four extremely powerful psykers were created, capable of theoretically wiping out the human race. However, the same changes that increased psychic ability also resulted in terminal insanity, forcing them to be sequestered and nullified to prevent them from harming themselves or others.

FEV Curling-13 strain
Based on the original FEV-II recovered by the Enclave at the Mariposa Military Base's ruins, FEV Curling-13 was a viral agent tailored to reach maximum levels of lethality with minimal exposure levels required to achieve the result. It was being developed under the direction of Lieutenant Colonel Dr. Charles Curling of the Chemical Corps since 2236, to provide the means for the Enclave's genocide. Just a .0001% aerosol solution exposure was enough to kill Arroyo villagers in under one hour, as massive hemorrhaging and inflammations start, leading to a complete failure of the victim's organs within sixty minutes. A significant radiation-induced mutation may thus be beneficial – humans with a lower radiation count suffer a much worse fate. Unmutated Vault 13 dwellers exposed to the virus experienced subdermal hemorrhaging and convulsions within sixty minutes of exposure, but their agony lasted much longer – 14.5 hours on average. No test subject survived the tests on Control Station Enclave.

Interestingly, in the event of worldwide release, only humans and human-based mutants would be eradicated, however – FEV was engineered to bond only with human glycoproteins, leaving other animals and plant life alive and unaffected. FEV Curling-13 is also unique in that it is the only known FEV strain for which an inoculation was developed that granted total immunity from its effects.

Modified FEV Curling-13
A modified strain of the Forced Evolutionary Virus developed by John Henry Eden, based on the earlier FEV Curling-13 strain used by the Enclave in 2241, only now it was designed to be placed into the Project Purity water purification system. According to President Eden it will eradicate super mutants, ghouls, and all other "unclean" citizens, namely anyone who had been born in the Wastelands and exposed to radiation or other mutational effects from birth. The only people who would survive the infection are dangerous radiation level free humans and humans who were born in the Vaults.

In the add-on Broken Steel, if the Lone Wanderer had chosen to contaminate the purifier with the modified FEV, what President Eden claimed is confirmed to be accurate and the FEV diffused in water completely lethal. The medical facility of every city in the Capital Wasteland (except Tenpenny Tower and Paradise Falls) is filled with new patients dying from FEV infection. These new patients hold their stomachs and repeat dialogue along the lines of, "it burns on the inside." According to both Doctor Preston and Doctor Barrows, the FEV specifically targets the immune system of infected individuals, which in turn makes them vulnerable to other diseases. This occurs in both humans and ghouls, despite the latter's immunity to most diseases. Along with affecting the immune system, the FEV severely weaken individuals both physically and mentally until it simply kills them. The modified FEV is also completely undetectable by any kind of test meaning there is no possible way to screen water that has been infected as it only comes back as clean, purified water.

The FEV is contained to only those that have ingested infected water as the transmission of FEV is impossible from physical contact or bodily fluids. In Rivet City, Dr. Preston comments that they are burning the corpses just to be safe. The spread of FEV is contained to only bottles of Aqua Pura and the Tidal Basin for now. However, eventually, the spread of the FEV infected water will spread from the Tidal Basin and affect all water in the Capital Wasteland.

Intelligent deathclaws
In 2235, the Enclave began experiments on captive deathclaws to create expendable shock troops for their use, continuing the pre-War project. The recovery of FEV from Mariposa allowed them to create a tailored mutagen that increased the intelligence of deathclaws after localized injections, making them capable of understanding and following complex commands, as well as communication. The resulting modification overshot the project goals, giving them human-level intelligence, erudition, and most importantly, morality. Realizing that they would be exterminated if that was discovered, Gruthar instructed his pack to play dumb until they were deployed to Vault 13. Although the Enclave intended to use them as deterrence, the deathclaws formed a commune instead, deserting their mission. Not all deathclaws were equally blessed with intelligence and some experienced further changes, including a gray skin and a bobtail.

All intelligent deathclaws were exterminated by a task force headed by Frank Horrigan, mopping the project up.

Fire ants
FEV was synthesized and used by Weston Lesko in the Capital Wasteland around 2277, in an attempt to return giant ants to their normal size through genetic manipulation. His ambition was to reduce their size exponentially over the course of several generations. An error in the synthesis process created a virus that left the ants' size unaltered but altered their venom sacks to produce a flammable liquid that they can aerosolize, project, and ignite with a spark generated by clicking mandibles. The resulting pyrosis, as he calls it, turns them effectively into walking flamethrowers.

History of the FEV
The Forced Evolution Virus originated from the Pan-Immunity Virion Project, a project originally dedicated to discovering a cure for the New Plague, was established in September 2073 in response to aggressive use of biochemical weapons by China. In order to combat the newest biological weapons, the decision was made to create a viral defense that would alter uninfected DNA to render it immune to standard viral infection. The last attempt to continue the PVP line of experimentation was the Greenhouse Initiative in August 2075 at the newly established Appalachian branch, which attempted to use mutations to create edible plants and vegetation that could greatly increase food production and combat the shortages that led to the food riots rocking the country. The town of Huntersville was selected as the test site, resulting in an economic boom. Although the company would purchase test rights from local farmers as late as December 2075, the project was at an end.

Batch 10-011 and the beginning of FEV
The history of the FEV starts with Pan-Immunity Virion batch 10-011, renamed as the Forced Evolutionary Virus (FEV) and used in further research. The key difference was that instead of Pan-Immunity Virion's quad-helix DNA structure, the batch became a shifting-absorptive virus. This was a deliberate choice by Major Barnett, who considered the unwanted side effects of the quad-helix structure to outweigh the benefits of replicative stability afforded by the design.

The first experiments took place in March 21, 2075 on single-celled organisms. While their base metabolism appeared unchanged, their immunity to infection and radiation exceeded all earlier expectations. Research on FEV effects on plants proved unsuccessful. The next stage included flatworms. Infected on May 9, 2075, they exhibited a 28% increase in size and resistance to 9 separate viral contagions within hours. The new DNA structure was successfully passed to progeny, though only asexual reproduction was possible.

June 30, 2075, saw the next stage of experimentation: several lab strains of white mice have been infected successfully with FEV. Within hours they exhibited increased growth, stabilizing at a 31% size increase after nine days. The most increase in size occurred in striated muscle tissue and certain internal organs, including the liver, heart, and kidneys. An increase in intelligence was also noted, allowing mice to run mazes in less than half the time required by normal mice.

The final experimentation with FEV batch 10-011 occurred with rabbits. On November 9, 2075, 218 rabbits were infected, half of which were implanted with electrodes to monitor changes in EEG activity. Increased electrical activity was noted 3.2 seconds after infection, accompanied by the typical increase in size. A new effect was noted, namely an increase in aggression and posturing, particularly among males. Dissection of the brains showed an increased dendritic connection, particularly in the limbic system and frontal cortex (areas responsible for behavior, senses and higher mental functions).

Batch 11-011 and nationalization
On January 6, 2076, West Tek was effectively nationalized after military units deployed to corporate facilities across the United States in the interest of national security. Experiments continued with Batch 11-011. The new virus batch featured improved mitotic cycle efficiency by a factor of 43%. As part of the test, 53 raccoons were infected with the new strain on January 26, 2076. Along with the expected size increase, behavioral tests confirmed an increase in intelligence and manual dexterity by 19 points on the Schuler-Kapp index. Unfortunately, subjects escaped confinement and had to be hunted down. Two pairs were unaccounted for.

In February, the West Tek facility in Appalachia joined the FEV research effort, ordered to begin human experimentation in order to push FEV to its practical limits, in what was dubbed the Super Mutant program. Due to the virulent nature of the virus and its unpredictability, the facility's objective was to identify and isolate viable FEV strains through a variety of methods. The most important of these was the introduction of one of the FEV strains to the water supply of Huntersville, to observe the effects of long-term low-level exposure. The experiment began in February 2076, providing valuable research data for the project.

Further development occurred after several new gene sequences, supplied by Major Barnett's advisory team, were spliced into FEV batch 11-011. Designated batch 11-101a, this batch was used to infect 23 dogs of pure and mixed breed on May 13, 2076. The results included nearly immediate growth, accompanied by increased aggression and no notable increase in intelligence. All subjects were terminated after 14 weeks of study. 92 allele pairs were chosen for splicing with batch 11-011.

Batch 11-111 and further human research
The new hybrid batch was designated 11-111. On October 4, 2076, it was used to infect 15 chimpanzees. Growth and immunity levels were unprecedented: attempts to induce cancers through radiological and chemical agents were not successful. Increased aggression led to isolating the subjects by the science team, while violent epileptic seizures caused two subjects to expire. The rest was terminated after all data was mined successfully. Despite protests from the science team, on January 7, 2077, FEV research in California was transferred to the Mariposa Military Base to continue under the lead of Leon Von Felden and Robert Anderson. Batch 11-111 has been chosen as the basis for further development through human experimentation. The batch offered a near 100% success rate on lab animals, granting an approximately 60% increase in size and potential 200% intelligence increase. It was the perfect basis for mass-producing super soldiers.

The Appalachian branch continued its experimentation by pushing FEV to its practical limits and experimenting with recombinant strains. The experimental strains resulted in the creation of many unsustainable forms: FEVS-005938 tested on January 13, 2077, rendered the subject unable to breathe, FEVS-006186 from April 30 converted the subject into a mass of retinal tissue, FEVS-006309 from July 12 produced canines that pierced the brain stem through unrestrained growth, and FEVS-006378 from July 12 was biologically stable, but the hyperactive nervous system subjected it to constant traumatic pain and led to self-termination. The team had more luck with strains FEVS-006443 (October 14) and FEVS-006458 (October 23) that created stable mutations that would become the snallygaster and the Grafton monster respectively after their escape into the wild.

Another research effort was set up by the Vault-Tec Corporation in Washington, D.C. Vault 87 was established as an independent research center for Dr. Wayne Merrick, cooperating with the team at Mariposa. Despite his efforts, he was unable to improve batch 11-111 enough to reach satisfactory effects. Humans subject to his strains produced in the Vault 87 labs exhibited superior physical developments, such as increased size, strength, and endurance to environmental factors, but were also characterized by significant mental retardation and extreme aggression to non-mutants.

Compared to Merrick's efforts and Appalachian experiments, the science team at Mariposa reached a full success. They succeeded in creating the FEV-II strain, able to create powerful super-soldiers, exhibiting superior physical prowess, resistance to combat damage, aging, and disease, as well as a negligible loss of intelligence. In certain cases, intelligence could even be increased by the virus. However, before the testing could begin in full, soldiers under the command of Roger Maxson rebelled and executed the science staff. With the Great War destroying the United States, Mariposa and research within was sealed by the soldiers and abandoned.

The Master
The vats were rediscovered in 2102 by an expedition led by Harold, a major Hub merchant. Accompanied by Richard Grey, a brilliant exile from Vault City, he managed to crack the Mariposa base security and infiltrate the lower levels. However, within the vats, the automated crane crashed into the two, knocking Harold out and flinging Grey into the vat with FEV. Harold woke up in the wastes outside the base, mutating due to exposure to FEV fumes, but becoming a special type of a ghoul-like mutant, rather than a super mutant. Grey, on the other hand, underwent extreme mutation due to prolonged exposure to the virus in the vat. His intellect grew exponentially, allowing him to comprehend even the most complex issues easily (or so he thought). Grey methodically researched FEV, experimenting with animals and eventually, captured scavengers that strayed into the facility. It was not until a few failed mutations that he discovered radiation count to be a deciding factor in the success of the change, leading him to pick subjects more carefully. When his Lieutenant was created, he suggested a secondary reason for possible incompatibility. Reviewing available evidence, he concluded that failed mutations in relatively non-radiated humans are caused by the inoculating effect mutated FEV had on humans with which it came into contact. Such exposure was not enough to cause phenotypical changes, but enough to cause conflicts when the pure FEV in Mariposa attempted to change the DNA, resulting in the death of the subject.

By carefully selecting his test subjects, he managed to create the first real super mutants in January 2103. Through a combination of willing converts and abductions, the Master slowly builds up the foundations for his army between 2103 and 2130. The impact of the Great Winter of 2130 results in him stepping up his operations and spreading them out into the wasteland, attacking caravans to gather human stock for transformations. The string of attacks between 2131 and 2135 boosts the size of his army. The attacks are blamed on desert monsters in the Hub. Due to reliance on wastelanders, only 20% of the dipped population survives the dipping and of that number, only half seem to last and become a part of the Unity. Regardless, it continues to grow.

By 2152, the Unity's influence has spread through the wastes and the Master recruited a group of doomsday cultists under Morpheus to act as spies, rather than stock for transformation. Four years later, the cultists would form the Children of the Cathedral to act as a front for the Unity, proselytizing, recruiting, and preparing munition dumps for the coming super mutant offensive. Between 2155 and 2156, the Master makes another important discovery: His forces intercept a caravan of vault dwellers, leading him to discover Vault-Tec's demonstration Vault. He moved his command center to the Vault, using the cultists to set up the Cathedral, and launched a campaign to discover Vaults to gain prime subjects for his super mutant army. At least one installation, Vault 17, was discovered and its inhabitants transformed into super mutants. The success rate is far higher than when using regular wastelanders. Even the elderly Lily Bowen was successfully transformed into a super mutant at the age of 75 - and a nightkin no less!

The Master and his staff also experimented with FEV by injecting it into the brains of the subjects (usually the pineal gland, but also the amygdala or medulla), triggering changes in brain chemistry. These experiments had limited success: four extremely powerful psykers were created, capable of theoretically wiping out the human race.

By 2161, the Unity was on the verge of achieving total military superiority over the human inhabitants of New California. All that was needed was Vault 13 and its inhabitants. Ironically, all FEV development and experimentation by the Master was abruptly halted by the Vault Dweller, of the very Vault the Master needed to dominate the New West.

The Institute
Commonwealth super mutants are the result of the Institute's research into FEV, which has continued since the early 2220s in a dedicated facility. The original goal was the creation of a successor to second generation synths by creating a new breed of super mutant that would serve the Institute as laborer and soldier. Due to a lack of success with mutants, efforts were refocused with the goal of creating third-generation synths. The organic synth project was spun off from the FEV research initiative around 2227 (the acquisition of Shaun), while the FEV research effort continued for several more decades. Both women and men were abducted from the Commonwealth and submerged in the Institute's modified FEV, their mutations carefully tracked. Successful mutations would be monitored to ensured survivability, then tagged and discarded. In layman's terms, the Institute was simply releasing super mutants into the wild, creating a scourge on the Commonwealth that lasted for years. When Brian Virgil succeeded Dr. Syverson as head of the project in April 2286, it became evident that FEV experimentation ran its course and served no useful purpose, not with the availability of third generation synths. Eventually, as Virgil's conscience took its toll, the scientist lodged a formal complaint with the Directorate. When no reaction came, Virgil rebelled and escaped the Institute after transforming himself into a super mutant, destroying as much of the project as he could.

The Enclave
Seeking the means to achieve their plans of global genocide, the Enclave excavated Mariposa from July to August 2236, in search of surviving samples of FEV-II. Using slaves captured in towns across California, they managed to uncover the vats and secure the necessary scientific material. However, slaves exposed to the raw virus in the ruins of the base mutated, creating the second generation super mutants. The uneven nature of exposure, coupled with a significant radiation count meant that those that survived the change suffered from significant mental damage. Retreating from the base, the Enclave blasted the only remaining entrance, trapping the mutants inside.

Enclave's Chemical Corps proceeded to work on the acquired samples of the virus, creating a staggeringly effective killer, tailored to provide maximum lethality with minimal required exposure. However, two weeks before the virus' deployment, the Enclave, and the virus stockpiles were destroyed. However, copies of research were transmitted to Raven Rock, providing Raven Rock's ZAX John Henry Eden with an opportunity to achieve plans of genocide. After modifying the FEV Curling-13 to only target the heavily mutated and heavily irradiated, the ZAX unit decided a localized infection of the water supply would be more effective at culling the undesirables while also improving the quality of life for the unmutated and unirradiated.

FEV in the Capital Wasteland
Despite Vault 87 being the main research facility, Dr. Weston Lesko found another source which he used to try to de-mutate the giant ants of the Capital Wasteland. As of 2277 his efforts culminated in the creation of fire ants. Also as of 2277, the levels of the said toxin were low in the vault, so the super mutants were actively searching for it in the surrounding areas.

Appearances
The Forced Evolutionary Virus or products of it appear in some form in all Fallout games to date.