Forced Evolutionary Virus

FEV or Forced Evolutionary Virus is a pathogen created before the Great War, used by various groups such as the Master, the Enclave, Vault-Tec, and the Institute.

Pre-War
To counteract biological weapons, the United States government began the Pan-Immunity Virion Project in 2073. The project aimed to alter uninfected DNA so that it was no longer susceptible to standard viral infection.

In March 2075, the virion was renamed FEV and Major Barnett ordered experiments focused on the quad-helix structure of the virus, which resulted in the subjects' immunity to infection and radiation exceeding expectations. Chloroplasts were not affected by the virus and Barnett canceled all future experiments concerning plant cells.

Throughout the rest of 2075 and 2076, the team experimented on flatworms, insects, mice, rabbits, raccoons, dogs, and chimpanzees. Side effects of abnormal growth rate and increased brain activity were noted in all subjects. The tests on dogs resulted in increased aggression without intelligence increase. The chimpanzee subjects were subjected to radiological and chemical agents in an attempt to create cancers, but these tests were unsuccessful.

Mariposa Military Base
In 2077, the military built a large facility in central California, the Mariposa military installation, to continue research on volunteer human subjects from the military. When the project was transferred in January 2077, the scientists who conducted the animal trials noted their disapproval regarding utilization of human subjects. Robert Spindel and Roger Maxson led the security team at the facility, but were not aware of the nature of work conducted there.

Once the inhumane nature of the research was discovered by the security team, Spindel suffered a nervous breakdown and Maxson took charge, attempting to handle the situation. He ordered the scientists to be interrogated, but many conversations let to executions, and the group subsequently abandoned the base.

West Tek research center
The virus was used in an experiment in Huntersville, resulting in the creation of mutants after the West Tek research center contaminated the local water supply with FEV in 2075. Various strains of the virus were used in experiments on both humans and animals in the Appalachian facility. Edgar Blackburn stated that observation, not a cure, was the purpose of their initiatives. He was not sure what the purpose of infecting the water supply of Huntersville was, apart from this observation, as they knew the virus in its current state "produced horrors."

Vault 87
Modified FEV was utilized as a part of the Vault 87 experiment. The scientists within the vault noted their efforts toward the Evolutionary Experimentation Program, or EEP, at the behest of Vault-Tec and the military members at Mariposa. Some strains caused fatalities, and causes of death were obscured from family members.

Characteristics
The virus is not airborne and only transferable via injection or direct physical contact with FEV samples. It copies DNA patterns, attempting to correct the DNA of the individual. The strain utilized in Vault 87 caused subjects of all genders to mutate into indistinguishable creatures, exhibiting identical muscle growth. Brain death was a result of certain strains, where others caused skin thickening, rage, and anxiety.

If the individual's DNA is damaged by radiation, it will cause organ failure and death. If the subject does not have pre-existing radiation damage, the virus causes an increase in muscle and brain mass, but also causes loss of memory. Prolongued exposure to the virus causes individuals to develop tolerances to its effects, preventing full mutation but still resulting in side effects such as skin tone changes, as well as increased strength and stamina.

The virus causes a painful transformation, but who are infected with the virus also experience side effects such as immunity to disease and radiation. Cell death is offset by augmented growth, extending lifespans indefinitely but causing sterility. Animals subjected to FEV grow larger in size in a short period of time. FEV cannot be removed once infection has occurred, but the Institute scientist Dr. Brian Virgil created a serum to reverse the mutation, called a retrovirus. Virgil stated that this serum would only work for one strain of FEV, and that generalizing the formula could take decades.

Vault 96
Blackburn continued his work after the war in Vault 96, utilizing human subjects abducted by a group of mercenaries called the Hellcat Company in an attempt to create "perfected FEV." Super mutants created were considered failures by Blackburn, and set free outside the vault.

Enclave FEV Curling-13
The Enclave Chemical Corps under Charles Curling isolated the most toxic elements of the virus found at Mariposa. An excavation team was sent to the location, shielded by protective suits, to find a supply of the virus. The team collected samples of the air and soil, both of which were contaminated by the virus. Local inhabitants were recruited to dig down into the facility, many of which began showing signs of FEV exposure.

Once a pure sample of the virus was obtained, Enclave scientists turned it into an even more fatal substance known as FEV Curling-13 that only impacted humans. Inhabitants of Arroyo and Vault 13 were kidnapped and subjected to tests, of which the vault-descendant subjects of the village were all killed using .0001% aerosol solution. Those from Vault 13 suffered subdural hemorrhaging and convulsions within one hour of exposure, and death within 14.5 hours.

Virus production goals were 250,000 gallons within six weeks, allowing for the murder of all non-Enclave residents in the area and around the globe, carried by the jetstream. An inoculation was developed that protected against the virus, tested on those taken from Vault 13. This immunity would be rendered to members of the Enclave staff via the air system and was also available by injection.

Enclave Modified FEV
The Enclave contingent in the Capital Wasteland utilized a modification of FEV at the behest of President John Henry Eden. This modified FEV was created in an attempt to murder individuals living in the area by contaminating the water supply using the Project Purity facility. President Eden states that the only people who would survive the infection are members of the Enclave and those who were born in the vaults. According to both Doctors Preston and Barrows, the modified FEV specifically targets the immune system of infected individuals on a cellular level. Barrows mentions that ghouls are usually immune to diseases, but are impacted alongside humans. The modified FEV is undetectable in water that has been infected.

The Institute
In August 2178, Dr. Frederick informed their colleague Dr. Elliott that the Directorate had pre-approved research on samples of the FEV virus which were already in their possession. Scientists within the Institute engaged in FEV research were able to adapt the two most promising strains of FEV to an ideal state by 2224, releasing successful creatures back to the surface, but research subjects were exposed to radiation, causing further progress to stagnate. Those working on the project such as Dr. Brian Virgil expressed their desire to close the project due to the lack of results, but were repeatedly denied.

In 2287, the Institute FEV lab is identified as a potential biohazard area and has been sealed following an accident. Madison Li stated that this explanation was unsatisfactory and the Director was not forthright with her concerning the situation. In actuality, the experiments ended when Doctor Virgil fled into the Commonwealth.

Behind the scenes
The Forced Evolutionary Virus is mentioned in the Fallout Bible.