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[[quoteright:350:http://static.tvtropes.org/pmwiki/pub/images/chucknorriszombie_3101.jpg]]
[[caption-width-right:350:When Creator/ChuckNorris is bitten by a zombie, he doesn't turn into a zombie. [[RussianReversal The zombie turns into Chuck Norris.]]]]

->''"Hey, Doctor Luce -- this proteus nanovirus -- isn't it supposed to, you know, go out of control infecting and transforming everyone, and like that?"''
->''"Of course not. Not unless you design it to. Here's how."''
--> -- '''''[[TabletopGame/{{GURPS}} GURPS: Bio-Tech]]'''''

There are forces, be they biological, mystical or technological, that can infect and change a person into something-- ''[[WasOnceAMan else]].'' These tend to be highly contagious, spreading easily via physical contact, bite, ritual, or other means. The changes are seldom subtle, and often [[TomatoInTheMirror quite a shock]] for the victim, who will likely [[WhatHaveIBecome wonder what they have become]]. On the plus side, the Viral Transformation is usually CursedWithAwesome, giving the "victim" {{Stock Superpower}}s ''and'' [[SuperEmpowering the ability to give them to others.]]

By now you're probably wondering what the downside is to this, and why this "[[CurseThatCures disease]]" hasn't been shared among all of humanity. Well, it's usually because it makes the transformees {{jerk|ass}}s. While it's not (always) TheVirus, making those infected into AlwaysChaoticEvil, {{Mind Control}}led servants to a HiveQueen who gladly [[ExoticEntree eats puppies]], it does lend itself to [[TheDarkSide "Power Corrupts"]]. Though the changes are mostly physical, the alterations may cause a change in perception because TheMindIsAPlaythingOfTheBody, their new body has a HorrorHunger only sated by [[PoweredByAForsakenChild eating orphans]] [[EvilTastesGood (and it tastes good!)]], and WithGreatPowerComesGreatInsanity.

Those responsible for infecting the victim may expect a FaceHeelTurn because the shock at the change will make them run to others like them, as well as FantasticRacism making it likely they'll be alienated by their friends and family (this is especially likely if the transformation is [[BodyHorror less than cosmetically appealing)]]. However; [[StagesOfMonsterGrief the choice to do so remains with the victim]]: they can consciously choose TranshumanTreachery, to stand apart and [[WhatMeasureIsANonSuper above of humanity]], become {{Fully Embraced Fiend}}s who enjoy their condition, to be FriendlyNeighborhoodVampires and live among if not entirely in harmony with humanity, or even be a ProHumanTranshuman and act the SheepInWolfsClothing while becoming a VampireHunter.

Common examples of this include most forms of [[OurWerewolvesAreDifferent Lycanthropy]] and [[OurVampiresAreDifferent some forms of Vampirism]]. Expect those affected by a Viral Transformation to be tempted to help friends or loved ones with an EmergencyTransformation or surprised when a blood donation turns into a SuperhumanTransfusion. See also VirusVictimSymptoms.

See also WarmBloodbagsAreEverywhere. Compare TheCorruption. A type of FaceMonsterTurn.
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!!Examples:

[[foldercontrol]]

[[folder:Anime & Manga]]
* ''{{Blassreiter}}''. After being infected with body-modification [[NanoMachines nanobots]] people become MadeOfIron and can meld with various hardware, but generally also turn into {{omnicidal maniac}}s with hallucinations and/or damaged memory. [[spoiler:Because the "[[HorsemenOfTheApocalypse Pale Rider]]" line of nanobots was designed this way and [[TheEndOfTheWorldAsWeKnowIt to that end]]. An original project was purely medical.]]
* Used in the Manga series ''Dragon Eye'', when the villains are created when the D-Virus changes them into a monster known as a Dracule. Anyone infected loses their identity and goes on a killing spree. Only a few, (about one in a hundred/thousand) have the antibody resistance that changes chance of infection from 100% to 10-0.1%.
* The Eclipse infection in ''MagicalRecordLyricalNanohaForce''. The good news is that, when infected, you gain powerful magic, HealingFactor, AntiMagic, [[PlotPoweredStamina inexhaustible endurance]], and a whole buttload of other stuff. The bad news is that, if you want to keep your life and sanity, [[HorrorHunger you need to keep on killing to keep the infection in check]].
* Becoming an Homunculus in the world of ''BusouRenkin'' sounds great - increased strength, a range of superpowers, {{Immortality}}, immunity to disease... but the fine print is that [[ImAHumanitarian your diet now consists of people.]] And if you're not a super-special-awesome Human-type Homunculus, you go insane and become dominated by your instincts.
* [[EverythingsBetterWithDinosaurs Scary Monsters]], the Stand-ability of Doctor Ferdinand from ''Manga/JoJosBizarreAdventure'': Steel Ball Run infects any living creature with a virus that turns them into a dinosaur under Ferdinand's control. Then the virus is spread by the dinosaurs themselves to practically create a [[ZombieApocalypse zombie infestation]]... of dinosaurs. Diego Brando is later able to keep and control the infection on him due to obtaining the [[PlotCoupon Saint's eye]] but Diego's version seems to lack the infecting properties.
* In ''Manga/{{Uzumaki}}'', most of the spiral transformations more or less come from out of nowhere and only hit a selected few individuals. However, the snail transformations seem contagious in their own way. The ones that start transforming into snails in the first place are always people who are physically slow, and then the ones who in any way hurt the snail people and/or their eggs will also be turned into snails.
* In ''Manga/AttackOnTitan'', [[spoiler: Titans are humans transformed through some unknown means -- Eren appears to have gained his powers through an injection, while the [[ManiacMonkeys Beast Titan]] employs an unrevealed method to transform an entire village. The majority are rapidly absorbed by their Titan form, becoming mindless horrors that devour other humans. However, some have control over it and gain a LovecraftianSuperpower with none of the urge to devour humans.]]
[[/folder]]

[[folder:Comic Books]]
* The Brood from [[MarvelUniverse Marvel comics]] propagate their species this way. They inject parasites into viable hosts (which is basically everyone) that gradually transform the hosts into more Brood. By the time the transformation's complete, the original psyche of the host is all but gone. Incredibly, despite being (nearly) AlwaysChaoticEvil, it's still possible to pity the Brood because this is the ''only'' way they can reproduce.
* ''Druuna'' comics have diseases that change people into tentacled monsters.
* The "Monstar Virus", pretty much ExactlyWhatItSaysOnTheTin, in the ''AmoryWars''. [[spoiler: Used to turn Coheed and Cambria into "The Monstar" and "The White Ruineer" respectively.]]
[[/folder]]

[[folder:Film]]
* ''[[Film/NightOfTheLivingDead George A. Romero's]]'' films cemented this concept with zombies and pretty much birthed the entire genre of the ZombieApocalypse. Many many ''many'' works have followed since.
* ''Film/{{Creepshow}}'' segment "The Lonesome Death of Jordy Verrill". After the title character is infected with liquid from a meteorite, he slowly changes into a fungus creature. He manages to end his suffering by committing suicide with a shotgun. The infection is later shown spreading across the countryside, creating a beautiful verdant landscape.
** The plot was obviously copied from H. P. Lovecraft's ''The Colour Out of Space''.
* ''Film/{{Underworld}}'' has examples of both this and TheVirus. The original flavor werewolves under William were all raving savages, but those who inherited it from Lucian spend most of their time in human form, and can eventually enter or leave were-form at will.
** Then you have the various takes on the hybrids. The movies show two different hybrids (Marcus and Michael) and mention a third (Lucian and Sonya's unborn child). The first two involve a member of one species getting exposed to the blood (and virus) of the other. While the viruses normally annihilate each other, the presence of the "Corvinus strain" in both allowed the viruses to merge into something new. In Michael's case, his original Lycan strain retained dominance, making him appear vastly more human than an average Lycan. Marcus, who started as a vampire, attained more bat-like characteristics, although he did gain several Lycan ones as well. It is unknown what Lucian and Sonya's child would look like, given that it was equal parts Lycan and vampire, or if it would survive at all, given the mutually-destructive "relationship" the two virus strains have.
* In ''Film/{{District 9}}'' this happens [[spoiler: to the main character after being sprayed with the alien "Fluid."]]
* In the 2001 Sci Fi Channel telefilm "Threshold" an astronaut infected with alien DNA let loose moth-like carriers that infected other people. The government found the hybrids all had B negative blood and, furthermore, the hybrids had stolen a list from a blood bank so they could track down their targets. The title comes from the other governments of the world declaring the invaders had to be stopped before they reached a critical population or Southern California would be nuked to stop them.
* In ''Film/{{Daybreakers}}'', humans are turned into vampires through a virus.
%% * ''Film/TheWolfman2010''
[[/folder]]

[[folder:Literature]]
* This is the basis for the ''Literature/WildCards'' series of books. An alien virus gives some people super-powers and transforms others into "Jokers", who are sometimes not even recognizable as having been human.
** Well, at least if your particular [[SuperpowerLottery draw]] included the ability to infect others. Despite the fact that ''xenovirus takis''-A was a ''literal'' virus, it wasn't (normally) communicable.
* Virals in ''Literature/{{The Passage}}''. Coupled with ''HorrorHunger''
* In ''Literature/{{Neverwhere}}'', spending too much time with people from London Below -- or if they "go too fast" around a [[{{Muggle}} normal]]-- will make the person go out of sync with people in London Above, making them InvisibleToNormals.
* In Jeff [=VanderMeer's=] ''[[Literature/{{Ambergris}} Shriek: An Afterword]]'' a fringe historian Duncan Shriek is the only human to discover a safe method to enter the underground realm of the Graycaps under the city of Ambergris, but this involved getting an esoteric fungal infection, which would in the course of the years transform him into [[BodyHorror a man-fungus hybrid]] who could only retain human shape through constant mental effort.
** The novel also features common people getting less extreme, though still bizarre-looking fungus infections out of the fungus bombs used during the civil war. And the sequel, ''Finch'', has Partials, people who voluntarily go through this process to become akin to fungus cyborgs.
* In ''Literature/TheRelic'' by [[Literature/AgentPendergast Douglas Preston and Lincoln Child]], [[spoiler: a reovirus creates monsters out of anything that ingests it]] by inserting saurian and reptilian DNA into host cells; but the victim needs a steady supply of specialized hormones to [[spoiler: retain its new form, the victim-turned-monster]]; in order to acquire these hormones, the victim must go right to the richest source available and ''[[HorrorHunger eat the hypothalamus]]'' of its victims or go mad from the pain of being unable to sustain [[spoiler: its new form]].
* It's very common in zombie novels for the zombification to be caused by a virus, the most famous or at least one of the earliest probably being ''Literature/IAmLegend'', both the book and movies.
* Happens to victims of the Flare, including [[spoiler:Newt]], from ''[[Literature/TheMazeRunner The Maze Runner Trilogy]]''.
* The virus in ''Literature/GalaxyOfFear: The Planet Plague'' turns people into [[spoiler: {{Blob Monster}}s]] which infect any bare skin they touch. The virus itself gets shown in a microscope-equivalent and is deliberately being tested and spread, to see how many [[NoBiochemicalBarriers species barriers it can jump]] after being modified.
* In the ''[[Literature/TheMortalInstruments Mortal Instruments]]'' series this is common from exposure to angelic or demonic influences and/or bodily fluids.
** The Shadowhunters received their special abilities from drinking the blood of the angel Raziel given to them in the Mortal Cup. New Shadowhunters can also be created this way, although the process is risky. [[spoiler: Jonathan Morgenstern arranged the creation of the Infernal Cup, tainted by the blood of Lilith, which can turn humans and Shadowhunters into [[EvilCounterpartRace Dark Shadowhunters]].]]
** Consumption of angel or demon blood generally, even in dried form, can result in changes to a person or their offspring. [[spoiler: Valentine, Jocelyn, Clary, Jace and especially Jonathan were all altered to some extent in this way due to Valentine's experimentation with the blood]].
** Vampires and werewolves are the descendants of two different species of demons. They can transmit their condition to humans, and even Shadowhunters, via bite.
[[/folder]]

[[folder:Live Action Television]]
* ''Series/DoctorWho''; ''The Empty Child/The Doctor Dances'' has people being transformed into zombie-like beings with gas-masks fixed on their heads. The cause are [[spoiler:alien medical nanorobots unfamiliar with humans, who took the first being encountered (a dead gasmasked boy) as a base template, and are now trying to "fix" the "sick" people. The problem is solved when the original boy's mother reveals herself and embraces her child. The nanobots figure out the correct human template and then quickly undo the damage.]]
** ''The Waters of Mars'' sees people touched with infected water turned into zombie like creatures that spray more infected water to spread the virus further.
** And the cliffhanger for ''The End Of Time part 1'' has [[spoiler: The Master utilizing a device called the Immortality Gate to turn every human being on Earth into versions of The Master (except for Wilfred Mott, whom the Doctor placed in a radiation-proof chamber and Donna Noble, who became half-Time Lord thanks to the events at the end of Series 4.]]
** In the classic series, we have the Krynoids. A Krynoid is a monstrous plant that [[spoiler: converts animal organisms into Krynoids by touch.]] Two men were converted in the Krynoids' debut story, ''The Seeds of Doom'' [[spoiler: not be confused with the earlier story ''The Seeds of Death'']]. This so outraged Mary Whitehouse, a media watchdog, that she spoke out about the "obscene vegetable matter" being shown on Doctor Who, which she dubbed "teatime brutality for tots".
** Of course the Vampires from Doctor Who story ''State of Decay''. Also the Haemovores, who are basically zombie-like aquatic vampires.
* The ''Franchise/StargateVerse'' loves this trope.
** ''Series/StargateSG1'': A virus caused people to turn into cavemen (a minor version, it just gave them funny foreheads and heightened aggression). A nanotech version made O'Neill 100 years old in a few days. Teal'c was bitten by a bug whose venom would have converted his total body mass into more bugs.
** ''Series/StargateAtlantis'': The Iratus bug retrovirus designed to "cure" Wraith does this. First it turned a female Wraith and then Sheppard into human/bug hybrids. Once perfected, it turned Wraith into humans. Michael, one such victim, took it and used it to make Wraith/human hybrids.
** ''Series/StargateUniverse'': [[spoiler:Chloe was infected with a virus by some aliens which appears to be turning her into one of them, or something close. At first it was mental, but then things got worse.]]
* Towards the end of ''Series/MaddigansQuest'', it's revealed that [[spoiler:Timon was injected with a virus based on [[BigBad the Nennog's]] DNA before being sent into the past. Once activated, it begins the job of turning him into the heir to the Nennog, granting him superhuman abilities, turning him evil and making him... less than entirely attractive (but, oddly, also more flirtatious than before).]]
* Ilyria was played as a variant of this on ''Series/{{Angel}}'', infecting Fred after she inhaled dust from Illyria's sarcophagus and then turning her slowly into the shell.
* ''Series/StarTrekEnterprise'' reveals that the Klingon loss of forehead appliques in ''Series/StarTrekTheOriginalSeries'' was due to a '''Viral Transformation''', and that they could eventually get better and regain their forehead appliques, in time for ''Film/StarTrekTheMotionPicture'' (and the other early 80s movies) and ''Series/StarTrekTheNextGeneration''.
* ''Series/TeenWolf'': Scott becomes a werewolf once Peter Hale bites him in the woods.
[[/folder]]

[[folder:Tabletop Games]]
* ''{{Cybergeneration}}'', a sequel to TabletopGame/{{Cyberpunk}}, is run on the premise that a nanite infection will kill anyone over the age of 16. If you're under 16 you survive... or change.
[[/folder]]

[[folder:Video Games]]
* Members of the [[BodyHorror Many]] in ''VideoGame/SystemShock 2'' undergo this, tending to leave behind a lot of {{Apocalyptic Log}}s. While some engage in TranshumanTreachery, a large amount of the creepiness is delivered by the poor {{Red Shirt}}s who ''[[AndIMustScream beg you to flee while they're unwillingly chasing you]]''.
* In ''LostSoulsMUD'', a local implementation of ''NetHack''[='=]s "eating a mind flayer makes you smarter" makes it so that eating the neural tissue of the vlekthid (read illithid) or gogtzul (read Star-Spawn of Cthulhu) races results in that neural tissue colonizing your own nervous system, making you smarter and less emotional, and giving you both psionic powers and often-crippling mental disorders.
* ''VideoGame/{{Borderlands}}''' first expansion, the horror movie themed ''The Zombie Island of Dr. Ned'', has both zombies and Wereskags (skags being the planet's equivalent to dogs/wolves). Both transmit their infection/curse via bites.
* Albert Wesker of ''VideoGame/ResidentEvil'' is infected with such a virus. It is not particularly transmissible, but it does make him something of an unstoppable badass.
* Redlight and Blacklight from ''VideoGame/{{Prototype}}''. Redlight is a completely straight version of TheVirus, which transforms people into braindead, malformed husks serving [[HiveQueen Elizabeth Greene]], while Blacklight is a ViralTransformation. [[spoiler:The player character, Alex Mercer is essentially a corpse reanimated by Blacklight, and although he is a {{Jerkass}} AntiHero with horrifying powers, he's significantly less evil than the real Alex Mercer was in life.]]
* Everyone is infected in ''VideoGame/Left4Dead''. If you're lucky, nothing about you changes and you become a carrier/survivor. If you're unlucky, you become a common infected. If you're EXTREMELY unlucky, you become a special infected.
* Mitochondria Eve of ''VideoGame/ParasiteEve'' fame is basically a sentient and controlled version of this by manipulating the mitochondria cells in any biological lifeform, whether it be man or beast. The beasts get some pretty wicked transformations. The humans however...[[SpontaneousHumanCombustion not so]] [[ImMelting much]]
* Played for laughs with Australium from ''VideoGame/TeamFortress2'', which induces TestosteronePoisoning upon those who use it. Specifically, this causes men to become incredibly muscular and grow impressive [[CarpetOfVirility body]] and [[BadassMoustache facial hair]]. As such, Australians in the setting are a race of hyper-advanced {{Boisterous Bruiser}}s with mustachioed women (barring the Mundy family).
[[/folder]]

[[folder:Web Original]]
* A SharedUniverse called ''The Blind Pig'' - and its reboot/successor [[http://shifti.org/wiki/Pig_and_Whistle Pig and Whistle]] - take place after a virus with unknown origins spreads throughout the Earth. A lot of the people who get it die. Some percentage of the survivors transform. A smaller percent of ''them'' get unusual abilities.
* The ''{{Paradise}}'' setting involves a "reality virus" that transforms humans into {{Funny Animal}}s at a rate that doubles every year.
[[/folder]]

[[folder:Web Comics]]
* In ''Webcomic/ElGoonishShive'', whoever touches the Dewitchery Diamond while under a "curse" (for a very loose definition of a curse) will be split into their normal state and a duplicate who not only is the embodiment of the "curse" as applied to the original person but who can spread it to others no matter what the nature of the curse is. Fortunately, if the "curse" is easily reversed, the people the duplicate transforms can have the transformation reversed just as easily.
* It's not exactly clear where all the "devils" in ''{{Sinfest}}'' came from, but at least some of them were originally human, and one of those has shown the ability to transform animals into their demonic equivalents. (Similarly, holy power can turn a devil human. The strip's version of Jesus spends a lot of time undoing transformations that its version of Satan has inflicted.)
[[/folder]]

[[folder:Western Animation]]
* In ''WesternAnimation/GeneratorRex'' when someone's (or something's) nanites activate they almost certainly become mindless killing monsters (called E.V.O.s) that try to attack anything and everything. You can also expect said monsters to be nightmarish and have a good bit of BodyHorror thrown in. And the rare E.V.O.s that retain their mind/personality/human appearence are people who you probably don't want to hang around with (except Rex). There are also those that turn into freaks but retain their personality, but they tend to either become victims of FantasticRacism or also be people you'd rather not be around.
** And said nanites that can mutate anything at any given time. They're omni-present and only the titular character can effectively cure aforementioned E.V.O.s.
* The Bio-mechs in ''WesternAnimation/VorTech'' were infected with a technological plauge transforming them into creatures much like the Phalanx in the X-Men comicbook titles.
[[/folder]]
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