An Infected Digimon (感染デジモン, Kansen Dejimon) is a Digimon who has been infected and taken over by a powerful force, causing them to completely lose control of themselves and run wild.
Infected Digimon are the result of digital data expressed in binary (i.e. 0s and 1s) or other systems being overwritten and converted into ternary (i.e. 0s, 1s, and 2s). Computer systems and data don't use ternary, so this causes serious errors in both the Digital World and the digital devices used in the Real World. This overwrite causes the appearance of distortions, and when it corrupts a Digimon it is the cause of the Infected state. The Infected Digimon are the first of the two problems caused by the overwrite, and the distortions began to appear after them.
Digimon are usually not affected by the infection immediately, but show symptoms of it with brief appearances of blinking purple static on their body. When an infection completely takes over a Digimon, something inside them becomes deranged, they completely lose their sense of self, and they will madly attack others like wild animals. This mad state can come as both brief fits which eventually end and can be resisted (for example, Leomon and Patamon), and as a permanent berserk state which cannot be reversed easily. Infected Digimon have blank eyes and are often colored with a purple tint.
In "Determination", Himekawa Maki reveals that Meicoomon is the cause of the ternary overwrite and, as a result, the distortions and the infection. She does not reveal this to the Chosen Children or their Digimon.
In "Confession", Homeostasis (in the body of Yagami Hikari) and Himekawa tell the partner Digimon that the threat of the Infected Digimon and the distortions is destabilizing the Digital World and the other realities, and that it is dangerously close to forcing a Reboot to occur, after which the crisis would be fixed as long as no traces of the Infected Digimon remain in the Real World. Izumi Kōshirō figures out that the overwrite is occuring and that it is the cause of the Infected Digimon. He also realizes that Meicoomon is the cause of everything, and the Chosen Children work to capture Meicoomon and stop the crisis. After most of the partner Digimon are taken over by the infection while fighting Meicoomon in her evolved form, Meicrackmon Vicious Mode, the Reboot is initiated while Herakle Kabuterimon has caught Meicrackmon, restoring the Digital World to a clean state and getting rid of all traces of the distortions and infections except for Meicoomon herself.
Digimon who have been infected
|Three Kuwagamon||One Kuwagamon realizes in Tokyo during the day and fights Yagami Taichi and Agumon. Two more realize that night at Haneda Airport. Two of them are destroyed by the Chosen Children and the third is taken back into the Digital World by Alphamon. ("Reunion")|
|Orgemon||Orgemon is infected while in the Digital World and realizes into the human world twice. The first time he fights the Japanese Disaster Responses Force, and the second time he fights Palmon and Meicoomon. Both fights end when Leomon pulls him back into the Digital World. ("Determination")|
Imperialdramon Fighter Mode
|This Imperialdramon is commanded by the Mysterious Man when he abducts Meicoomon. ("Determination") According to both forms' Digimon Adventure tri. First Memorial Set cards, this Imperialdramon is infected, though this isn't mentioned in the movie.|
|Leomon||Leomon begins to be affected by the infection when Imperialdramon appears. He resists the infection and helps Vikemon and Rosemon to fight Imperialdramon, but is killed by Meicoomon when he has a brief fit of madness after the fight. ("Determination")|
|Meicrackmon: Vicious Mode||According the Digimon Adventure tri. First Memorial Set Meicrackmon is infected. ("Confession")|
|Patamon||Patamon is the first of the Chosen Children's partner Digimon to show symptoms of being infected. He begins experiencing fits of madness early on and is taken over by the infection during the fight with Meicrackmon, while evolved to Angemon. ("Confession")|
|Piyomon||Piyomon is taken over by the infection during the fight with Meicrackmon, while evolved to Birdramon. ("Confession")|
|Gabumon||Gabumon is taken over by the infection during the fight with Meicrackmon, while evolved to Garurumon. ("Confession")|
|Palmon||Palmon is taken over by the infection during the fight with Meicrackmon, while evolved to Togemon. ("Confession")|
|Gomamon||Gomamon is taken over by the infection during the fight with Meicrackmon, while evolved to Ikkakumon. ("Confession")|
|Tailmon||Tailmon is taken over by the infection during the fight with Meicrackmon, while evolved to Angewomon. ("Confession")|
|Agumon||Agumon is taken over by the infection during the fight with Meicrackmon, while evolved to Metal Greymon, and is the last partner Digimon to become an Infected Digimon. He evolves to War Greymon while controlled by the infection. ("Confession")|
|Tentomon||Tentomon shows the symptoms of being infected, but the Reboot happens before he is taken over by it. ("Confession")|
|Mugendramon||This Mugendramon is commanded by the Mysterious Man. ("Loss") According to Re-53t this Mugendramon is infected, though this isn't mentioned in the movie.|
|MetalSeadramon||This MetalSeadramon is commanded by the Mysterious Man. ("Loss") This Digimon is known to be infected due to being the same as Mugendramon.|
Jijimon tells Takuto/Shiki that something strange, likely a Digimon from another World, had been picked up in Mod Cape. They are sent to investigate, assuming that it is Meicoomon, as the tamer had already befriended her in the past. Upon arrival to Mod Cape, the Agumon (Black) that usually roam on the ship are all knocked out. The tamer is able to wake them up, though they have no memory as to why they had been knocked out, or even as to why they are on the ship, showing they all have amnesia. Once an antivirus is used on them they remember that they saw a strange looking Digimon, covered in a black aura and that upon seeing her, they all "started to feel fuzzy" and then blacked out. After helping the Agumon (Black), the tamer is sent a message that the signal had now been picked at in the Infinite Cauldron. Once there, the tamer finds a Were Garurumon (Black), who had been defeated in less than 10 seconds. Once the tamer offers to help heal him though, he suddenly is cloaked in a purple aura and attacks the tamer's partners. After defeating the WereGarurumon, the tamer uses an anti virus on him which causes him to regain control of himself, then explains that a strange looking orange fuzzy Digimon covered in a black aura appeared, which caused him to feel fuzzy and he attacked it in self defence, only to be quickly defeated.
The tamer is sent to Server Desert next where Meicrackmon Vicious Mode is found, currently in the process of fighting and infecting Yukimura and Rikka. When Yukimura attacks Meicrackmon, Meicrackmon yells out that she will not forgive White Fang and teleports away. Luckily though, Yukimura had managed to gain a small amount of the black aura. When Luche touches it, the aura is destroyed, showing that Luche is immune to it and is able to neutralise it. They come up with a plan for Tsuzuki Shoma and Noir distract it, whilst Luche applies an anti virus made out of her DNA and whilst the aura is being neutralised, Takuto/Shiki's partners swoop in to defeat her. The group finds Meicrackmon in the same place that Meicoomon had originally been found. The plan works and after being defeated, Meicrackmon regains control and realises she is back in the Next Order Universe, as it was not her first time there. The "White Fang" intended to use Meicoomon for evil, so captured her and Mochizuki Meiko, her partner, fell into a trap on purpose allowing her to escape. When Meicoomon tried to free her, the White Fang used a machine that caused her to evolve and then cross dimensions, with the shock of dimension hopping causing her to suffer from amnesia, causing her to lose control and attack everyone she came across. Luche's DNA causes Meicoomon to be cured of the Infection. Meicoomon then returns to the Adventure Universe, using the power of her bond with Meiko and then frees her from the White Fang.
Digimon who have been infected
|Three Agumon (Black)||Three Agumon (Black) are infected by Meicrackmon, though are cured by Mameo's anti virus.|
|Were Garurumon (Black)||A WereGarurumon (Black) is infected by Meicrackmon, though is cured by Mameo's anti virus.|
|Meicrackmon: Vicious Mode||Meicrackmon is infected, and infects other Digimon, though is cured by Luche's DNA.|