The FOXDIE virus enters macrophages in the target's bloodstream, then uses enzymes to attach to a DNA sequence that it has been "programmed" to recognize. Once the virus is attached to the DNA, the macrophage starts to produce the cytokine TNF (tumor necrosis factor) epsilon. The TNF-epsilon is carried along with the blood, to the heart, where it binds to the TNF receptors, causing the myocardial cells to die. This programmed cell death is called apoptosis, which leads to the victim suffering a heart attack. Natural heart attacks occur when the heart cells die from lack of oxygen and sugar, usually caused by a blocked coronary artery.
The development of the FOXDIE virus was one of the Pentagon's biological weapons programs. The FOXDIE program 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. Since then, the virus has been altered and re-created several times.
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.
Snake eventually discovered that Naomi had made an alteration to the virus so that at an unknown point in time it would also kill him, as an act of revenge for "killing" her closest relative, Frank Jaeger. When asked by Snake, regarding the amount of time he had until the virus killed him, Naomi replied, "Live, Snake. That's all I can say to you." Since Naomi had set the virus to activate at a "wildcard" value, she was unaware of when exactly he would die. However, it was later revealed that this FOXDIE wouldn't kill Snake, due to genetic variation inherent in the Les Enfants Terribles project, which differentiated his DNA code from that of Liquid 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, as well as his infection of it from Naomi, was briefly mentioned by Snake during the Tanker Incident in 2007, when he stated that he was glad that while he is in Philanthropy, he won't have to worry about being given any "unwanted gifts." 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 brainfather of FOXDIE) 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.
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 the old FOXDIEEdit
Victims of the new FOXDIEEdit
Behind the scenesEdit
Naomi's character profile on the official Metal Gear Solid 4: Guns of the Patriots website, along with the Metal Gear Solid 4 Database, erroneously state that FOXDIE was created by the CIA. In Metal Gear Solid: The Twin Snakes, Revolver Ocelot claims that he survived the events on Shadow Moses due to the FOXDIE vaccine, in his phone call to Solidus Snake, though the Database states that it is unclear whether or not it ever actually existed. In addition, in Ocelot's call to Solidus for both Metal Gear Solid and its remake, The Twin Snakes, Ocelot explained that the vector (Solid Snake) was set to be activated soon, although whether this was meant to imply that they arranged for Naomi to edit FOXDIE or not is never elaborated on.
In Metal Gear Solid, FOXDIE was spelled "FoxDie." Subsequent games and sources spell it in capital letters.
In the Grand Game Plan for Metal Gear Solid 2, it was implied that Solidus was intended to be a target for FOXDIE by the Patriots, but he had received the vaccine and thus was immune to Snake's FOXDIE.
When Big Boss explained that the true cause of deaths for Ocelot and EVA were in fact the new FOXDIE strand injected into Snake when explaining that he's been infected with it, a series of flashbacks also included Naomi among EVA and Ocelot.
It is important to note that the new FOXDIE did not affect Ocelot while in his Liquid persona, as it only started to take effect when his original personality resurfaced. Liquid Ocelot does, however briefly fake out Snake in Act 4 by re-enacting his death from Metal Gear Solid.
In the PlayStation-exclusive Deja Vu mission for Metal Gear Solid V: Ground Zeroes, when Classic Snake/Big Boss arrives at the tiger cage where MGS1-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 Skin or the 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 referencesEdit
- ^ 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 4 Database, Kojima Productions (2008). 
- Metal Gear Solid 2: Sons of Liberty (Indirect mention [Tanker Chapter]; mentioned [Plant Chapter])