- "FOXDIE is a type of retrovirus that targets and kills only specific people."
- ―Naomi Hunter
The FOXDIE virus enters macrophages in the target's bloodstream, then uses enzymes(integrase, primarily) to integrate its genetic material into a DNA sequence that it has been "programmed" to recognize (this last part being the difference between it and an ordinary retrovirus, which may display a tendency to integrate at certain sites but cannot be "programmed" to target specific sequences exclusively). Once this genetic material is integrated into the host cell chromosome, it promotes TNF (tumor necrosis factor) epsilon production in the host. The TNF-ε is carried along with the blood, to the heart, where it binds to the TNF receptors, causing apoptosis in myocardial cells, which in turn leads to the victim suffering a heart attack. The only difference between this and natural heart attacks is that the latter occur when the heart cells die from lack of oxygen and sugar, usually caused by a blocked coronary artery, rather than TNF-ε-induced apoptosis. Rate of infection can also vary depending on the infected person's age: Namely, it's more likely to affect older subjects faster than younger subjects.
FOXDIE, however, cannot actually bypass any protective barriers to the respiratory system, and targets who are addicted to anti-depressants such as pentazemin will have the virus be significantly delayed in affecting the circulatory system. This is evidenced by how Psycho Mantis and Sniper Wolf, respectively, were able to avoid being infected by FOXDIE prior to death. In addition, a vaccine was rumored to exist to evade the virus entirely.
The development of the FOXDIE virus was one of the Pentagon's biological weapons programs. The idea for a weapon that could eliminate specific individuals by targeting genes, was conceived by Patriot founder Zero as early as 1976, in response to the Philosophers' "ethnic cleansing" vocal cord parasites, which he deemed obsolete. The FOXDIE project was led by the DIA operative Richard Ames under the authority of President George Sears, and under orders of the Patriots. The FOXDIE virus had been in development as the research hit a wall until 2003 when Dr. Naomi Hunter joined the project. When the virus was successfully engineered, it was Naomi who named it FOXDIE. Since then, the virus had been altered and recreated several times.
- Main article: Shadow Moses Incident
In February 2005, the Pentagon ordered Naomi to inject FOXDIE into an unassuming Solid Snake, shortly before his mission to Shadow Moses Island. The virus was programmed to kill the renegade members of FOXHOUND, who had taken over the island's nuclear disposal facility, as well as ArmsTech President Kenneth Baker. This was carried out in order to eliminate both the terrorists and anyone else involved on Shadow Moses, and to allow recovery of the hijacked Metal Gear REX, dummy warhead data, and the bodies of the Genome Soldiers, intact. Baker had some awareness of FOXDIE's development, but did not anticipate that it would actually be deployed. After becoming infected, Baker attempted to warn Snake of the virus upon deducing the cause of his sudden heart attack, but was unable to before drawing his last breath.
FOXHOUND commander Liquid Snake learned of FOXDIE's existence through a spy in the Pentagon, and added a FOXDIE vaccine to his list of demands to the U.S. government. Solid Snake eventually discovered that Naomi had made an alteration to FOXDIE so that it would also kill him, as an act of revenge for crippling her adoptive brother, Frank Jaeger.
Following Liquid's death from infection by the virus, Solid Snake inquired as to his own survival, given his similar genetic code, to which Naomi replied, "Live, Snake. That's all I can say to you." Since Naomi had set the virus's incubation period to a random value, she was unaware of when exactly he would die, although FOXHOUND spy Revolver Ocelot (having himself survived due to access to the vaccine) was under the impression that it would activate in Snake relatively soon after the Shadow Moses Incident. However, Naomi believed since FoxDie was programmed to kill Liquid, it would kill Snake as well due to their genetic similarities, even though it was never programmed to kill him. This was not the case since despite being clones of Big Boss, their genome was manipulated to have distinct differences. These differences would end up being enough for FoxDie to only target Liquid, but not Snake.
Nastasha Romanenko received an optical disc, containing all the records of the personnel and research pertaining to the FOXDIE project, from her ex-husband Ames. He willingly gave it to her in an attempt to keep her safe from the Patriots by using the disc's contents as leverage in case they tried to harm her. Shortly thereafter, she used the contents of the disc to explain the true events of the Shadow Moses Incident in a book called In the Darkness of Shadow Moses: The Unofficial Truth.
FOXDIE was briefly referenced by Snake during the Tanker Incident in 2007, when he stated that he wouldn't have to worry about being given any "unwanted gifts" while operating as part of Philanthropy. In 2009, a digital version of FOXDIE was uploaded into the GW AI of Arsenal Gear. Designed by Emma Emmerich to disrupt GW's operating system and render it unusable in case it fell into the wrong hands, it was altered just before the incident by the Patriots to delete any data about their "true" identities. The computer virus was part of the S3 Plan that manipulated the events of the Big Shell Incident into an orchestrated recreation of the Shadow Moses Incident. Besides the worm cluster, the Patriots also remotely deactivated Ames' (ironically the leader of the FOXDIE project) nanomachines when Ocelot discovered him, in order to ensure that he died in a similar manner to Decoy Octopus and Kenneth Baker before him.
After the SOP System was developed, it incorporated the nanomachine base for FOXDIE, namely as a strict genetic lock for the System to prevent it from being hacked.
The biological FOXDIE that was still in Old Snake began to mutate when his body started to age at an accelerated rate. This new FOXDIE would eventually lose its ability to kill based on specific DNA sequences and would begin to kill people at random, possibly becoming a worldwide pandemic. Snake learned of this after Naomi Hunter conducted medical tests on him in 2014, the latter of whom also noted the irony that Snake's last moments may result in him becoming one of the weapons of mass destruction he had attempted to destroy throughout.
It later became apparent, however, that Snake had previously been injected with a newer form of FOXDIE by Drebin during his failed mission to assassinate Liquid Ocelot in the Middle East, which halted the mutation of the original virus. The new FOXDIE was programmed by the Patriots to kill Big Mama, Liquid Ocelot and Big Boss. Although the new FOXDIE had uprooted the old, it would eventually mutate as well and become dangerous to the general population. However, this would not occur for several years, and would only live as long as Snake, which was an estimated year at best.
Other than the mutated and new strands of FOXDIE, Liquid Ocelot briefly alluded to his earlier death from FOXDIE shortly after being defeated in a Metal Gear battle with Snake on Shadow Moses, including re-enacting how he had earlier died, albeit with the phrases used reversed. However, Liquid then got back up and revealed he had been faking before telling Snake that FOXDIE "won't work on him this time."
Victims of FOXDIE
Behind the scenes
The original FOXDIE virus appears in Metal Gear Solid. In the English version, the name of the virus is rendered as "FoxDie." Subsequent games and sources, excluding Metal Gear Solid: The Twin Snakes, render the whole name in capital letters.
In The Twin Snakes, Revolver Ocelot claims that he survived the events on Shadow Moses due to the FOXDIE vaccine, in his conversation with Solidus Snake following the game's end credits, although the Metal Gear Solid 4 Database states that it is unclear whether or not it ever actually existed. Both the Database and Naomi's profile on the official Metal Gear Solid 4 website mistakenly identify the CIA as FOXDIE's developers, rather than the DIA.
According to Hideo Kojima's "Grand Game Plan" for Metal Gear Solid 2, it was intended that Solidus would be a target for Snake's FOXDIE by the Patriots, but was immune due to having received the vaccine.
In the Japanese version of Metal Gear Solid 3: Snake Eater, FOXDIE is referenced by pun, when Naked Snake asks Major Zero, "Will our 'FOX' die as well?" (俺たちの「ＦＯＸ」も死ぬのか？?). The word play was lost when translated in the English version ("Does this mean FOX is going to die?").
In Metal Gear Solid 4: Guns of the Patriots, Ocelot did not succumb to FOXDIE while in his Liquid persona, despite having been in close proximity to Solid Snake during Act 3. The virus only started to take effect when his original personality resurfaced in Act 5.
In the Déjà Vu mission for Metal Gear Solid V: Ground Zeroes, when Classic Snake/Big Boss arrives at the animal cage where Metal Gear Solid-era Donald Anderson is being held, the latter starts experiencing convulsions mirroring that of FOXDIE while also yelling "FOXDIE!". Finding Kenneth Baker at the admin building's boiler room will have the same effects. Note that they only appear as Anderson and Baker, respectively, if the player is playing with the Classic Snake or Cyborg Ninja skin. Upon encountering both POWs and witnessing their deaths, the player will end up "infected" with FOXDIE, causing the game to glitch up and experience psychedelic colors with computer code in the background before being "rebooted" by the Fox Engine. In addition, after completing all the quiz questions post-mission, Liquid will end up succumbing to FOXDIE, with the player having to complete Liquid's statement as the "eleventh" question.
Notes and references
- ^ a b c Metal Gear Solid 2: Sons of Liberty, Konami Computer Entertainment Japan (2001).
In the Darkness of Shadow Moses: The Unofficial Truth 
- ^ Metal Gear Solid: The Twin Snakes, Konami Computer Entertainment Japan (2004).
- ^ Metal Gear Solid 2: Sons of Liberty, Konami Computer Entertainment Japan (2001)
Otacon: The private sectors not so bad, is it? Privacy guaranteed… // Solid Snake: I’m happy as long as no one gives me any more unwanted gifts. // Otacon: You mean that thing with Naomi?
- ^ Metal Gear Solid: The Twin Snakes, Konami Computer Entertainment Japan (2004).
Revolver Ocelot: Yes... Yes, sir. Thanks to the vaccine.
- ^ Metal Gear Solid 4 Database, Kojima Productions (2008). 
- ^ http://www.tentenpro.com/muni_shinobu/mgs3/commentary.html
- Metal Gear Solid
- Metal Gear Solid 2: Sons of Liberty (mentioned)
- Metal Gear Solid: The Twin Snakes
- Metal Gear Solid 3: Snake Eater
- Metal Gear Solid Mobile (mentioned; non-canon)
- Metal Gear Solid 4: Guns of the Patriots
- Metal Gear Solid V: Ground Zeroes (Déjà Vu mission; non-canon)