This trope is for [[ExactlyWhatItSaysOnTheTin viruses of the mind]]. They spread the same way as any other normal virus, either through exposure to someone who's already infected or through some airborne particulate. However, unlike normal viruses, they primarily don't cause any physical symptoms. Instead the virus will alter the way its victims ''think''.

[[MindVirus Mind Viruses]] can vary in terms of their effects and their severity. Minor cases might simply give the victims [[PsychicDreamsForEveryone weird dreams]], or give them a [[CompellingVoice slight compulsion to do something]] (though this compulsion can be ignored with enough willpower). More severe Mind Viruses can do everything from [[FakeMemories alter]] or [[LaserGuidedAmnesia completely erase]] memories, [[NotHimself alter one's personality]], or even completely [[MindRape destroy someone's mind]], leaving them a shell.

[[MindVirus Mind Viruses]] usually don't have anything to do with [[{{Brainwashed}} brainwashing]] or [[MoreThanMindControl mind control]]. A nefarious agency may have developed and released the virus, but after that the virus is uncontrolled, spreading from one person the the next in an unpredictable manner. Rather, a deliberate MindVirus may be used as a ''weapon'', intended strictly to disrupt. Alternatively, it might have started off [[UtopiaJustifiesTheMeans with good intentions]] but [[FreakLabAccident ended up mutating and spreading out of control]].

This is a trope usually found in Science Fiction, though not necessarily limited to it. In nearly all cases it's a SyntheticPlague. A specific version of this would be a HatePlague. Not to be confused with TheVirus, a trope where a contagion acts as an intelligent, self-directed entity (adding to "itself", having a HiveMind, etc). Compare InfectiousInsanity, a trope where mental illnesses is treated like a MindVirus, and EarWorm, where it's a song that can't get out of your head. See also ScienceRelatedMemeticDisorder, which is often -but not always- caused by one of these.

In RealLife, there's a sociological model known as [[http://en.wikipedia.org/wiki/Memetics Memetics]], which posits that information and culture behaves like genetics ("meme" being the informational analogy of "gene")--that units of information transmit themselves from mind to mind. There's other competing sociological models, some of whose proponents point to MemeticMutation as an example that Memetics isn't a viable model.
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!Examples:
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[[folder: Anime and Manga ]]

* In ''HigurashiNoNakuKoroNi'', [[spoiler:Hinamizawa Syndrome]] is caused by some sort of parasite that is initially compared to a virus in the sixth arc. That is the only arc where it is referred to as a virus, and the person who called it that was an UnreliableNarrator. The arcs after it tend to use the term parasite. Since there are many lifeforms (and viruses) that can theoretically be called parasites, it's a little uncertain what type of lifeform it actually is. [[spoiler:That parasite, though, is what causes just about all of the madness that winds up killing so many people in the earlier arcs]].
* In ''GhostInTheShellStandAloneComplex 2nd Gig'' the "Individual Eleven" virus infected people who read a certain essay, becoming terrorists and (aside from Kuze) eventually committed suicide.
* In ''Manga/MagicalRecordLyricalNanohaForce'', anyone who infected with Eclipse become an Eclipse Driver that knows nothing but kill to survive.

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[[folder: Comic Books ]]

* An issue of ''ComicBook/TheAuthority'' had Apollo and Midnighter teaming up with alternate-universe versions of themselves to stop a killer meme: anyone who heard it would whisper it to the first person they saw and then commit suicide. They had to stop the meme from making its way to a TV studio, where it would be spoken on a live broadcast. [[spoiler:The solution is to subject it to ExecutiveMeddling, which renders it harmless.]]
** Also the Godhead arc, which featured a villain with the power to turn people into his slaves.
* In one ''Franchise/{{Batman}}'' StoryArc, the villains try to release a meme virus into the population of Gotham which will give everybody a predisposition to addiction, thus causing chaos.
* In ''ComicBook/{{Planetary}}'', the BigBad's power is seemingly that his mind expands and 'infects' other minds near himself, causing them to start to think the same way and become, well, ''him''. It ends up becoming an InformedAbility because we never see him use it.
* ''ComicBook/{{Transmetropolitan}}'' alludes to things like this at times, although details for how they work are never given. A [[ImAHumanitarian Canibalism Meme]] is mentioned as one point, for instance.
* Came up in a section of [[ComicBook/TheLeagueOfExtraordinaryGentlemen the Black Dossier]], in which a descendant of Fu Manchu tried to release an (ancient Aztec) linguistic virus into a Massachusetts spaghetti restaurant to perpetuate a feud between his family and Professor Moriarty's. [[MakesJustAsMuchSenseInContext Makes far, far less sense in]] [[Creator/TheBeatGeneration context]].

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[[folder: Film ]]

* In the film ''Film/{{Pontypool}}'', the English language becomes infected with a virus that drives English-speakers crazy.

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[[folder: Literature ]]

* Creator/AlastairReynolds features these prominently in many of his novels. ''Century Rain'' has the "Amusica" virus that causes its victims to be unable to appreciate music (released as a demoralizing tool in a war). ''[[Literature/RevelationSpaceSeries Chasm City]]'' has a communicable virus that inflicts its victims with the memories of a religious cult leader, giving them dreams of his life and causing stigmata to appear on their body.
* Creator/CharlesStross has this in the novel ''[[Literature/{{Accelerando}} Glasshouse]]''. A virus called "Curious Yellow" has infected nearly all humans, via the ubiquitous and necessary [[PortalNetwork Warp Gates]] that everyone uses to get around. It deleted memories of a recent war, giving pretty much everyone amnesia of that specific time period. Furthermore, it also deleted the memories of ''who released it'' and its full extent, meaning that nobody knows what ''else'' it might've done (or still be doing).
* ''Master of Space and Time'' by Rudy Rucker has a section where the heroes visit an alternate dimension full of "meme viruses". One of the characters is bitten by a "Jesus Lizard" and subsequently starts gaining [[MessianicArchetype messiah-like characteristics]], along with [[HippieJesus growing out his hair and beard and wearing sandals all the time]].
* In Kathleen Ann Goonan's ''Queen City Jazz'', part of her "Nanotech Quartet" series, a nanotech apocalypse sweeps across the world. There are several nanotech mind viruses going around, such as a virus that compels its user to [[DisappearsIntoLight go to one of several glowing spheres]] that have cropped up around the country. Further, the main character in ''Mississipi Blues'' is infected with a virus that compels her to abandon her old life and go rafting down the Mississippi river ''a la'' ''Huckleberry Finn''.
* The third book in the ''Literature/PlagueYearSeries'' by Jeff Carlson, ''Plague Zone'', features a mind virus that turns its victims into mindless husks that wander around, attempting to spread the virus to others (through airborne contact). They're not ''violent'' or anything, but insistent, shambling about like living zombies that don't eat or attack.
* Creator/PeterWatts' ''Literature/RiftersTrilogy'' features several mind viruses, most notably "[=GuiltTrip=]", which forces its victims to always do "good" things (and severely punishes them, through pain or death, for failing to do so). A government agency purposefully infects its employess with [=GuiltTrip=], reasoning that by doing so they do not have to worry about security anymore, since nobody would dare attempt to subvert or steal anything.
* There is a short story by RobertSheckley where everyone on Earth learns to levitate. If, however, they ever doubt their ability to levitate, they lose it. Additionally, if one person sees another who is unable to levitate, it would automatically plant doubt into ''their'' minds as well, in effect becoming a fast-spreading virus.
* ''Literature/SnowCrash'' features a "biolinguistic virus" that renders its victims unable to communicate normally; anytime they try to talk, they just speak gibberish.
* Creator/GregBear's novel ''Vitals'' features bio-engineered viruses that manipulate their victims hormones and brain chemistry. Though the viruses themselves are undirected, the [[TheOmniscientCouncilOfVagueness evil government conspiracy]] will "dose" people with different strains of the virus, in combination with setting up fake evidence, in order to discredit anyone who threatens to expose the conspiracy. One character, an investigative author who starts getting too close to the truth, is infected with a compulsive anti-semitism virus that causes him to lose his reputation. Later on, another character is made to murder by use of a HatePlague. The main character is also infected with a kind of "love" virus that renders him dopey and lovey-dovey with respect to a woman who's an agent of the conspiracy.
* In one ''Homer Price'' story, the town gets infected with a song. A mysterious stranger comes to town and puts a record in the donut shop's jukebox, telling Homer and his friend [[SchmuckBait not to play it]]. Of course they do, and they [[EarWorm can't stop singing the song]]. They teach the song to others, who can't stop, and so on. Homer finally cures himself and the town by learning a different song (from a MarkTwain story), which makes them forget the first song, and once you pass that song on you forget it in turn. They send the one person infected with the new song out of town (she was going on vacation anyway) where they hope she'll teach it to someone else.
* "Hostess", a short story by Creator/IsaacAsimov, suggests that humans die of old age because they're infected by a parasite that exists in their mind (it having adapted to not even needing a body). By the end, it's indicated that many of humanity's [[HumansAreSpecial unusual traits]] are caused by the existence of the parasite.
* In ''Literature/TheCuriousIncidentOfTheDogInTheNighttime'', the hero fantasizes of a virus ("like a computer virus") that spreads by people looking each other in the face. He is heavily autistic, and thus would survive such an epidemic.
* Though the "culling song" in Creator/ChuckPalahniuk's ''{{Lullaby}}'' starts out as a lethal BrownNote, it eventually turns out that merely thinking about it can telepathically transmit it to someone else, making it a lethal Mind Virus.
* John Barnes's ''Candle'' portrays the near-total success of one such virus, with only one remaining human being in the world who isn't infected. [[spoiler:He has a different virus instead.]]
* NeilGaiman's poem ''[[http://www.scribd.com/doc/7227151/Gaiman-Neil-Virus Virus]]'' is an example of this, spread via a computer game.
* Creator/VernorVinge's ''Literature/RainbowsEnd'' has the YGBM ("You Gotta Believe Me") virus, the hunt for which is a major plot of the book.
* In ''Literature/ThoseThatWake'', this is how Man in Suit propagates himself.

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[[folder: Live Action TV ]]

* The ''Series/StarTrekVoyager'' episode "Flashback" featured a virus in the form of a fake memory which spread through mental contact.
* The Sickness in ''Series/{{Lost}}'', which is how The Man in Black recruits people to his side.

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[[folder: Music]]
* The ''Music/AbneyPark'' song ''[[https://www.youtube.com/watch?v=4lmLQRhVqr4 Virus]]''.
-> ''It feeds on the souls of the living.''
->''And gets inside their minds.''
->''Transforms their brains and their longings,''
->''No consciousness it will find.''

->''It feeds on their fears and emotions,''
->''As it has for 2000 years''
->''Its infected the Hindus, infected the Buddhists,''
->''Kept them all in tears.''
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[[folder: Other ]]

* The Game. It even has an [[http://xkcd.com/391 antivirus]]!

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[[folder: Tabletop Games ]]

* Some forms of the Exsurgent virus in ''TabletopGame/EclipsePhase'' simply alter how the victim thinks and/or add PsychicPowers, turning them into an unwitting pawn of the TITANS.
* In ''TabletopGame/{{Paranoia}}'', rumor has it that Viral Thought Patterns are behind Communism, Gamma Clearance, and Computer knows what else. (Rumors are treason. Report all rumors.)

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[[folder: Video Games ]]

* The Maverick Virus and it's upgraded verson the Zero Virus from ''VideoGame/MegaManX'' both infect Reploids and alter their programming, turning them into murderous psychopaths that still, for the most part, retain their memories and personality. The Sigma Virus, on the other hand, is a sentient entity that [[BodySurf takes over]] other Reploids and appropriates their bodies.

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[[folder: Visual Novel ]]

* The entire premise of ''VisualNovel/LuxPain'' revolves around fighting the spread of [[MindVirus Mind Viruses]].

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[[folder: Web Comic ]]

* In ''Webcomic/SchlockMercenary'', the Macarena is referred to by Reverend Theo Forbus as a "[[http://www.schlockmercenary.com/2009-10-14 proven memetic infector]]."
* ''AMiracleOfScience'' never goes into the exact details of how one normally contracts ScienceRelatedMemeticDisorder in-universe (it's implied to be more of a "GoMadFromTheRevelation" scenario, but never really discussed in-depth), but the [[HiveMind Martians]] express concern that if one of their citizens contracts it, it might become one of these to them. It's only a theoretical possibility, but one they're understandably unwilling to test.

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[[folder: Web Original ]]

* The Wiki/SCPFoundation has quite a few of these, which are classified under ''Memetic Hazards''. "Infohazards" and "cognitohazards" are similar; where one starts and one ends is very much a DependingOnTheWriter thing.
* In ''OrionsArm'' [[http://www.orionsarm.com/eg-topic/45b41654cd0c4 memetics]] are a mature science.

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[[folder: Western Animation]]

* Mentioned in WesternAnimation/YoungJustice. When Artemis drugs (and is subsequently attacked by) an evil telepath when on deep-cover, she uses this as an explanation for his odd behaviour.

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[[folder: Real Life ]]

* RichardDawkins is the originator of the term "meme" and the concept of memetics. As an avowed atheist, he's written a number of articles and books using his model to liken religion to a disease--even outright labeling it as a "mind virus" in ''The God Delusion''. Calling religion a "mind virus" has subsequently become popular among "New Atheists," who tend to be fans of Dawkins.
* The early stages of ants infected with ''[[http://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis Ophiocordyceps unilateralis]]'', AKA the zombie fungus. The ant is physically unchanged, but begins exhibiting odd behaviors like seizing out of its nest, climbing up the nearest suitable plant, and chomping down on a leaf so hard that it remains fixed there permanently while the fungus grows. As the fungus progresses, however, it takes over the ant's body physically as well as mentally - as fungi tend to do with decomposing organisms.
* The [[http://en.wikipedia.org/wiki/Dicrocoelium_dendriticum lancet liver fluke]] is capable of controlling ants as well. Normally, ants retreat into their nest at night, but when a fluke gets in control of one, it causes the ant to climb up to the top of the nearest blade of grass and clamp its jaws down on it in hopes that the parasite's next host - a large herbivore - will mistakenly consume the ant along with the grass. However, the ant doesn't die as it does with the fungus; if it isn't consumed by an herbivore, it will instead climb down from the grass at dawn and continue to go about its daily ant activities, only to climb back up the grass at the next sunset.
* Humans infected with ''Toxoplasmosis'', a protozoan found in cat feces, have been shown to have several oddities in their behavior (up to the point that CrazyCatLady might ought to be renamed Toxoplasmosis Infectee). Infectees can develop mental symptoms that resemble schizophrenia, and some, particularly men, are known to lose their aversion to the stench of cat urine such that a dirty litterbox no longer bothers them. ''Toxoplasmosis'' also has an acute disease phase which resembles more traditional ills, with fever and malaise and the like, but it's the latent phase which is this trope.
** Humans aren't the only ones who are affected by the infection. Rodents with ''Toxoplasmosis'' in their brains spend an excessive amount of time running around to draw attention to themselves and completely lose their fear of feline scents, even seeking them out. This serves to get the ''Toxoplasmosis'' into a cat, which is where it really wants to be.
* Rabies is best known for its "furious" state, in which the virus drives the host to actively and violently seek out victims to bite. This is, of course, to insure its own transmission. The other thing it's known for is hydrophobia, an irrational fear of water (which serves no purpose other than to weaken the infectee such that they will die sooner and infect fewer new victims).
* The phenominon termed ''[[GratuitousFrench folie deux]]'', or [[http://en.wikipedia.org/wiki/Folie_%C3%A0_deux shared psychosis]]. For those who are susceptible to madness, simply being around another unstable person can not only trigger a psychotic episode but can cause their form of madness to come to resemble the other person's, meaning that a form of mental illness normally thought of as self-limited suddenly becomes contagious.
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