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[[quoteright:350:[[{{VideoGame/Infectonator}} https://static.tvtropes.org/pmwiki/pub/images/patzeviii_8321.png]]]]
[[caption-width-right:350:Well, that escalated quickly!]]

TheVirus has taken over the entire world/country/town. Almost always, there is a patient zero. This is the person that started it all, the very first person to be infected. Perhaps they carried the virus for a while without realizing they were a ZombieInfectee. Perhaps they were the one who created the virus.

Sometimes, you have to kill patient zero to stop the virus before it spreads to anyone else. Other times, Patient Zero carries the original, unmutated virus, which the heroes need to FindTheCure. If the Patient Zero is asymptomatic and/or doesn't know what they're carrying, they may be a TyphoidMary or ZombieInfectee.

----
!!Examples:

[[foldercontrol]]

[[folder:Comic Books]]
* The Patient Zero in ''ComicBook/AfterlifeWithArchie'' is technically Jughead's dog Hot Dog after he is brought back to life by magic, but the first human zombie is Jughead after Hot Dog bites him.
* In the ''ComicBook/{{Crossed}}'' arc "The Thin Red Line", it is revealed that [[spoiler:there were several Patient Zeros for the virus in different parts of the world, suggesting an unnatural origin for the disease. The British Patient Zero plays a major role in the story, while others in France, Australia, and Chad are mentioned]].
* In one ''ComicBook/JusticeLeague2011'' story, a failed assassination attempt on Lex Luthor releases a virus from his lab that causes those with super powers to become very sick and gives super powers to normal people which eventually kill them. The original purpose of the virus was to take super powers away. The Justice League hunts down Patient Zero, Armen Ikarus, who has grown into a monster with multiple superpowers, hoping that they can make a cure from them, but this doesn't work. Instead, a cure is made from Superman, who has antibodies against the virus because Lex Luthor had previously infected him with it, but his immune system had fought it off and he hadn't spread it to anyone.
* ''ComicBook/{{PS238}}'': An AlienInvasion targets humanity with a contagious virus intended to [[TheVirus turn humanity into more of themselves]], but due to a lack of NoBiochemicalBarriers the virus had to be tailored to the specific body of the first human the aliens abducted, which turns out to be [[spoiler:Tyler. Luckily, he is put into stasis fast enough, and is later cured by a blood transfusion from someone with IdealIllnessImmunity]].
* In ''ComicBook/TheSmurfs'', Grouchy Smurf is the original carrier of the Black Smurf virus that very nearly wipes out the Smurfs (old enough to be an UrExample of ZombieApocalypse), and it's given as an explanation for why he is so grouchy (he's the first to catch the virus and the last to be cured). In [[WesternAnimation/TheSmurfs1981 the TV adaptation]], it's Lazy Smurf who is Patient Zero of the Purple Smurf virus.
* In ''ComicBook/XMen'', reference is made to 'Patient Zero' of the mutant-killing Legacy Virus, who was apparently a mutant who contracted the virus and released it into its airborne form when he used his power for the first time after becoming infected. Eventually, Beast was able to devise a cure, but the only way to release it on a large scale was to 'infect' someone else with the cure, which would kill the host just like the original virus killed Patient Zero (although Colossus chose to use it anyway).
* ''ComicBook/ZombiesChristmasCarol'' has Scrooge contract the Hungry Death from a horse, which rotted after administering the bite, and then he became the carrier to the rest of the world.
[[/folder]]

[[folder:FanWorks]]
* ''Fanfic/EverfreeInfectionAU'': Twilight Sparkle is explicitly identified as the first to have been infected, having picked up spores from the fungus-overgrown remains of a mouse.
[[/folder]]

[[folder:Film]]
* ''Film/ArmyOfTheDead'': Richards was a soldier involved with experiments at Area51 that led to him becoming "Zeus", the Alpha King of the zombies that overran UsefulNotes/LasVegas once he broke out of containment.
* In ''Film/Contagion2011'', Patient Zero is Beth Emhoff [[spoiler:although technically the true Patient Zero is the chef that handled the infected pig as shown in a flashback at the end of the movie.]]
* In ''Film/{{Cooties}}'', the patient zero for a kids-only zombie virus is Shelley Linker, who contracts the virus from an infected chicken nugget. Shelley goes on to infect a bully named Patriot and his friend Dink, the latter of which infects all but two kids in the school during recess (one because they were studying in the library, and the other because of post-pubescent immunity).
* ''Film/EbolaZombie'''s patient zero died prior to the backstory, but infected her daughter along the way. Her scientist husband is SupportingTheMonsterLovedOne by keeping the daughter alive in secret while trying to prevent a full-scale outbreak, but naturally everything goes wrong.
* In an obscure French movie titled ''Film/{{Goal of the Dead}}'', patient zero is Jeannot Beleaux, who his father inadvertently infects with a zombie virus after its package gets switched with steroids. Jeannot goes on to infect and kill multiple people in town, before exponentially spreading the virus to a majority of townspeople during a football game.
* In ''Film/TheKillerThatStalkedNewYork'', a 1950 film {{Very Loosely Based|OnATrueStory}} on the [[https://en.wikipedia.org/wiki/1947_New_York_City_smallpox_outbreak 1947 New York City smallpox outbreak]], patient zero is Sheila Bennet, a diamond smuggler who brings smallpox into New York City from Cuba. The authorities scramble to find her after the outbreak has started in order to keep her from spreading the disease to even more people and to be able to find out who she has already been in contact with. This is quite a change from the RealLife outbreak, where patient zero was not a smuggler but a regular tourist, did not get infected in Cuba but in Mexico, and was not the subject of a contact-tracing manhunt but was rather admitted to hospital before the outbreak really began.
* In ''Film/{{Outbreak}}'', Patient Zero is a wild monkey carrying the Motaba virus; the first ''human'' infectees are Jimbo Scott and the pet store owner he was trying to sell said monkey too -- the latter of whom got scratched while handling the animal, the former of whom got spat on by the monkey while releasing it into the wild. Though Jimbo only ends up spreading the virus to his girlfriend before snuffing it, the pet store owner ends up infected with an airborne strain of Motaba... and ends up spreading it to everyone in his town.
* Naturally this is the object of the scientists in ''Film/PatientZero2018'' in their hidden underground lab, with most of the human race infected. [[spoiler:Unfortunately, it's the object of the more intelligent Infected as well, to eliminate this threat to their survival.]]
* In ''Film/ProWrestlersVsZombies'', killing the two zombies raised by ritual seemingly causes all of the other zombies to vanish.
* The memorable opening scene of ''Film/ResidentEvilAfterlife'' with the J Pop Girl with ThousandYardStare standing in the rain at the Shibuya Scramble Crossing who [[DeadlyLunge suddenly chomps]] on a passing Japanese salaryman, followed by the lights going out across Tokyo and [[SpreadingDisasterMapGraphic then the rest of the world]].
* In ''Film/RiseOfThePlanetOfTheApes'', Franklin is Patient Zero for what will become known as Simian Flu. Unfortunately for all, it's an airborne virus, and he managed to infect a pilot before he died. [[spoiler:''Film/DawnOfThePlanetOfTheApes'' reveals that only 1/10th of the population survives, most with a natural immunity to the virus.]]
* In ''Film/WorldWarZ'', Patient Zero is what the main characters are searching for. [[spoiler:They never find it.]]
* In ''Film/{{Zombieland}}'', Patient Zero is said to have been a person who ate a bad hamburger. Mad cow disease then became mad human disease.
* Indian zombie comedy flick ''Film/ZombieReddy'' has the hero's friend, Bhadram, getting bitten by an unnamed man he unintentionally runs over, and thinking nothing of it. Turns out the person is a carrier of some zombie virus, and soon Bhadram begins biting a random maid, who goes on to bite a worker, until a massive outbreak occurs full-swing.
* In ''Film/{{Zoombies}}'', patient zero is a monkey named Sandy, who dies and reanimates in a lab. The monkey then spreads the virus to three other monkeys offscreen. Once the monkeys escape the lab, the rest of the zoo’s animals become infected more or less instantly. Another similarly premised movie, ''Aquarium of the Dead'', has an octopus as the patient zero, although the rest of the animals becoming infected is At least justified given this would be a waterborne disease.
[[/folder]]

[[folder:Literature]]
* ''Literature/TheBelgariad'': A chapter midway through ''The Mallorean'' dives into AndNowForSomeoneCompletelyDifferent, telling the story of [[AssholeVictim a thieving sailor named Balsca]]. After stealing from and deserting his ship, he sleeps with a young woman afflicted with an unknown disease on the street. After waking up to the woman's grinning, dead face, he makes his way to the imperial city of [[TheEmpire Mal Zeth]], where our protagonists are currently [[GildedCage staying]] within the citadel. The plague spreads through the lower levels of the city, [[FromBadToWorse and things kind of go downhill from there]].
* Vergil Ulam is patient zero of the noocyte outbreak in ''Literature/BloodMusic'', being both the first infectee and the creator of the noocytes. He is killed in an attempt to prevent the outbreak.
* Patient Zero of the Blue Pox in ''Literature/CircleOfMagic: Briar's Book'' was a stupid mage who became infected after improperly disposing of a failed weight loss potion. She was discovered dead in her study.
* The events of ''Literature/EdenGreen'' are made possible by Tedrin, the first human infectee of an alien needle virus. Since it renders him immortal (and insane), he's only too happy to spread it to others.
* In the ''Literature/{{Fablehaven}}'' series, [[spoiler:Ephira the tree spirit]] was the first victim of the demon Kurisock's corrupting power, the Shadow Plague. She'd been corrupted for a while (due to a [[DealWithTheDevil supernatural bargain]] with Kurisock) before getting her hands on an AmplifierArtifact that allowed her to spread TheCorruption to others.
* In ''Literature/FelicityFlooVisitsTheZoo'', Felicity is the one who initially has a cold (or possibly the flu), but then she spreads it to all the animals.
* The pimp in the ''Literature/{{Illuminatus}}'' trilogy, who is unaware that he carries the deadly virus and who sparks a panicked manhunt. Fortunately, he has gone to ground, terrified of arrest after the death of a working girl and after having acquired top-level secrets. He is found dead in a cave.
* It's proposed by a Rokkau that the true cause of TheVirus in ''Literature/JanitorsOfThePostapocalypse'' is that during FirstContact, there was [[FirstContactFauxPas some sort of altercation]] between a venomous [[OctopoidAliens Rokkau]] and one of the human leaders. The venom put her into a comatose state. Human scientists created a viral agent affecting her brain and body that got her moving and eating again, but it spread from there, killing half of the people who contracted it outright and converting the rest into {{Technically Living Zombie}}s.
* In Creator/JohnRingo's ''The Last Centurion'', an illegal Chinese immigrant provides the vector that gave the [=H5N1=] virus a path from China (the source of the virus) to the US.
* Subverted in the ''Literature/{{Newsflesh}}'' universe, in which there is no known Patient Zero for Kellis-Amberlee. There were not quite 100 living Marburg Amberlee patients when the Kellis virus was released and combined with MA, which had recently started spreading to those close to the original patients. Factoring in incubation periods, the combination had plenty of time to spread before [[ZombieApocalypse the Rising]] began in multiple places almost simultaneously.
* A subject in Creator/{{Amoridere}}'s ''Sneezing Blood'' (and its sequels) becomes this when she sneezes blood into a crowd of people, which exposes them to whatever she's sick with and things go south from there. By ''Quarantined'', the doctors start wondering how she works as living host for it, as everyone else that caught it died.
* In ''Literature/TheStand'', Charles Campion can be considered Patient Zero, in that he's the one who gets out of the base and spreads the superflu virus along his path from California to Texas.
* ''Literature/WorldWarZ'' plays with the trope a bit. "Patient Zero" is apparently a young boy in China, who was diving for salvage in the reservoir where his family's home village used to be and came up bleeding heavily and missing a toe. If we take everything in prequel-of-sorts ''Literature/TheZombieSurvivalGuide'' to be canon for ''World War Z'', the only possible source of the infection is another zombie, possibly from a former Chinese military biological warfare programme. However, ''The Zombie Survival Guide'' seems to exist in a universe where the zombie virus is a known, scientifically documented phenomenon with a long history of outbreaks stretching back at ''least'' to AncientEgypt, yet in ''World War Z'', humanity is almost entirely blindsided. The precise origin of the outbreak is therefore unclear, with "Patient Zero" merely being the first ''known'' ZombieInfectee.
[[/folder]]

[[folder:Live-Action TV]]
* In the ''Series/{{Community}}'' episode "[[Recap/CommunityS2E06Epidemiology Epidemiology]]", Patient Zero is Pierce, being the first person to eat the tainted "taco meat".
* ''Series/DoctorWho'':
** Jamie in "[[Recap/DoctorWhoS27E9TheEmptyChild The Empty Child]]"/"[[Recap/DoctorWhoS27E10TheDoctorDances The Doctor Dances]]" is Patient Zero of the gas-mask zombie plague.
** In "[[Recap/DoctorWhoS35E9SleepNoMore Sleep No More]]", much is made of the Patient Zero of the Sandman plague, the first person Dr. Rassmussen tested his anti-sleep experiments on. [[spoiler:It turns out to be an InvokedTrope, designed to give the Doctor a narrative where he stopped the plague and preventing him from discovering the ''real'' vector: [[TheFourthWallWillNotProtectYou the recording you just watched]].]]
* Parodied in part one of the ''Series/GirlMeetsWorld'' episode "Girl Meets the Ski Lodge" in the Rucas scenario when Maya says that Riley is suffering from "Gooey Sap Disease" and she's marked as patient zero, which in turn leads to a sudden death of the other couples ([[MyFriendsAndZoidberg and Cupid Auggie]]) near her.
* In ''Series/{{Helix}}'', the CDC rapid response team's best guess is that research scientist Peter Farragut is the first human infectee of NARVIK-B, TheVirus and SyntheticPlague that turns its victims into super-strong [[NotUsingTheZWord Vectors]] compelled to infect others. However, the staff at Arctic Biosystems, the remote research base where the outbreak is occurring, refuse to tell the whole story, and from the rantings of Vectors, other scientists likely [[TestedOnHumans went before him]].
* The ''Franchise/KamenRider'' series has two examples:
** In ''Series/KamenRiderExAid'', Patient Zero for the Bugster virus is [[spoiler:Ex-Aid himself, Emu Hojo]] -- in fact, he was infected a full year before the medical community even knew the virus existed, meaning he flew under the metaphorical radar. This explains quite a few mysteries surrounding his character, including [[spoiler:why Emu could transform without undergoing the "compatibility surgery" (read: getting vaccinated) required to become a Kamen Rider and the apparent SplitPersonality between his compassionate doctor side and his hardcore gamer side]]. It turns out that Emu isn't the only Patient Zero for the Bugster virus; there is another one, [[spoiler:Masamune Dan/Kamen Rider Cronus, who is revealed to have infected himself with the virus sixteen years ago, the same time Emu was infected. Thanks to that, he has the same level of immunity and compatibility as Emu, which is what allows him to transform into Cronus]].
** In the second season of ''Series/KamenRiderAmazons'', the protagonist Chihiro/Kamen Rider Amazon Neo is revealed to be [[spoiler:the source of Lysogenic cells virus that causes normal humans to mutate into a new breed of mindless man-eating Amazons]].
* In the ''Series/{{NCIS}}'' episode "[[Recap/NCISS11E11 Homesick]]", the team searches for the origin of a mysterious epidemic among the children of soldiers on Christmas Eve, with over thirty kids being infected and an elderly dry-cleaner having died of it. [[spoiler:The origin turns out to be a Marine Captain who had come back from a special assignment to Africa not long before, who plays Santa Claus on Military Christmas parties and who infected the dry-cleaner when collecting his Santa suit. The epidemic turns out to be a meningococcus strain only found in Africa, and with that knowledge, all the infected kids can be saved.]]
* ''Series/TheOuterLimits1995'': In the future shown in "[[Recap/TheOuterLimits1995S7E2PatientZero Patient Zero]]", humanity is ravaged by a plague. A man travels back in time to the present to kill the plague's patient zero to prevent the plague from happening. Because patient zero turns out to be a beautiful woman, the man can't bring himself to kill her, and instead decides to protect her and prevent her from getting sick in the first place. [[spoiler:Eventually, another time traveler shows up and reveals that in his efforts to prevent the girl from becoming sick, the man himself has become sick and become the new patient zero. The man agrees to be killed, which successfully stops the plague.]]
* In ''Series/PersonOfInterest'', Finch refers to himself as this in regard to knowledge of the Machine, as he built it. This isn't an actual disease, but since the government tends to arrange for fatal accidents to happen to anyone they think is even considering leaking information about the Machine's existence to the public, it's no less deadly.
* In the ''Series/Sanctuary2007'' episode "Pavor Nocturnus", [[spoiler:Magnus]] is the first carrier of the virus that turned almost everyone into cannibalistic monsters.
-->'''[[spoiler:Helen]]:''' I was patient zero.
* In the ''Series/{{Sliders}}'' episode "[[Recap/SlidersS01E03Fever Fever]]", Quinn's double is Patient Zero for the "Q", with a million-dollar bounty on his head. It turns out that the plague is nothing more than a hard-hitting bacterial infection, which is lethal here because this alternate Earth never developed penicillin.
* In ''Series/StarTrekDeepSpaceNine'', Section 31 creates a [[SyntheticPlague devastating virus]] that afflicts Changelings, hoping to bring about a Changeling genocide. The group infects Odo without his knowledge. The virus is spread by linking, so Odo unwittingly passes the pathogen to other Changelings while in the Great Link.
[[/folder]]

[[folder:Video Games]]
* ''VideoGame/AnnieLastHope'' opens with an unnamed drunk in an alley getting ambushed by the crabs -- small, insectoid critters carrying the undead virus -- and quickly converting into a zombie. He might or might not be the first victim of the upcoming apocalypse, though, since in the next cutscene a hundred zombies suddenly appears in a party to infect everyone.
* One of the abilities of Beatrix from ''VideoGame/{{Battleborn}}'' which is actually named Patient Zero turns either herself or a targeted into a contagion carrier that deals damage to nearby enemies for a short time whilst also having their speed buffed. Her ultimate Outbreak as well has her plague a targeted enemy into a contagion carrier. While affected, the plagued enemy lose health, are wounded, and the healing they receive is reduced. These effects spread among nearby enemies.
* In the ''VideoGame/FalloutNewVegas'' DLC ''Old World Blues'', Patient Zero of the spore virus found in Vault 22 is a miniboss that can be encountered. There's also the Lobotomite Test Subject 1.
* ''VideoGame/GoingIntoTheUnknown'' revolves around a zombie virus outbreak that wipes out a town. [[AllThereInTheManual According to the backstory]], the first ZombieInfectee is a young girl who contracted an unidentified viral strain, and the resident doctor, Adam, decide to keep her in a psychiatric ward when she mindlessly tries attacking him. And then she escapes and infects everyone, and the outbreak quickly goes out of control.
* The GOTY Edition of ''VideoGame/Hitman2016'' brought in the Patient Zero campaign, which has 47 and Diana race against the clock to stop a virus spreading. The campaign starts in a hotel in Bangkok, which has 47 kill the cult leader who has created the virus. However, 47's actions triggers a DeadMansSwitch, and he must get a vial of the virus from an author in Italy, Sapienza, who plans to give it away to a cult member. You then move onto Colorado to take out mercenaries via sniper rifle in a farm-turned military compound, and kills the doctor testing the virus on various mercenaries (whom you must also take out). Then we come to Hokkaido, Japan, to kill the man who wants to spread the virus. That last mission is called "Patient Zero" also. You also need to kill any other people infected.
* ''Infected: The Twin Vaccine'' is all about locating a six-year-old who's the only known survivor of a virus which first hit her and her twin sister so that the title vaccine can be produced.
* ''VideoGame/InfinityWars'' has a card named [[http://www.aletasarchive.com/images/cards/IW2013_PATIENT_ZERO.png?d=20140507 Patient Zero]]. Sure enough, he's the origin of the zombie nanovirus on his world.
* The [[MeaningfulName appropriately named Zero]] of ''VideoGame/MegaManX'' was designed by [[MadScientist Dr. Wily]] to be the original carrier of the Maverick Virus, the very virus that makes Reploids go berserk in the first place. As such, not only is he himself immune to the virus, [[BeneficialDisease he also gains benefits from said virus whenever it enters his system]].
* Melissa Pearce in ''VideoGame/ParasiteEve''. [[spoiler:Late in the normal game, you find out that Aya's dead sister was actually the ''original'', true Eve. The original appears in the optional dungeon as the TrueFinalBoss.]]
* Naturally, being a game where the goal is to kill the world with a disease, ''VideoGame/PlagueInc'' makes mention of a Patient Zero. In a side event the CDC may try seeking Patient Zero out in hopes of better understanding the disease.
* The reanimated corpse of [[spoiler:Doctor Alex Mercer, a.k.a. Blacklight, protagonist]] of ''VideoGame/{{Prototype}}''. [[spoiler:Elizabeth Greene]] is also one, carrying her own Redlight virus.
* In ''VideoGame/StubbsTheZombie'', you play as a dead salesman reanimated by experimental fertilizer spread over his shallow grave as he turns a city into zombies.
* ''VideoGame/TraumaCenterAtlus'': The final chapter in ''Trauma Team'' is even called Patient Zero. It involves [[spoiler:finding the girl whose blood originally carried both Rosalia and its antibody]].
* ''VideoGame/Vampyr2018'': The patient zero for the Skal epidemic (a plague that turns humans into mutated, feral vampires) is revealed to be [[spoiler:Harriet Jones, who was being experimented by Dr. Swansea using vampire blood to cure the Spanish influenza. What he didn't expect is that Jones was also an WalkingWasteland possessed by [[BigBad the Red Queen]] to spread disease and [[TheScourgeOfGod punish mankind for its inequities]]]].
* The indie game ''VideoGame/ZombieSimulator'', sees you as the first zombie who begins with escaping the bio-lab you're locked in, and then infecting the staff before controlling an entire zombie horde to overwhelm an entire city.
* In ''VideoGame/ZombiesRun'', [[spoiler:Patient Zero is Patient 29 of 50 patients who received an injection that was supposed to make cells regenerate faster]].
[[/folder]]

[[folder:Visual Novels]]
* [[spoiler:Rika Furude]] of ''VisualNovel/HigurashiWhenTheyCry''.
[[/folder]]

[[folder:Webcomics]]
* In ''Webcomic/ManlyGuysDoingManlyThings'', Patient Zero for [[{{Bishonen}} the Nomura Virus]] was ''VideoGame/NieR''. The related anti-Nomura effect [[VideoGame/BreathOfFireII Ryu]] suffered from was a curse rather than a contagious disease, and the [[WesternAnimation/MyLittlePonyFriendshipIsMagic ponifying effect]] that [[Film/TheBigLebowski Walter]] suffers from was a poison, so while both are the first known patients, their respective syndromes won't spread.
* In ''Webcomic/StandStillStaySilent'', the apparent Patient Zeroes of the Rash Illness that caused TheEndOfTheWorldAsWeKnowIt were a group of eleven illegal refugees arriving in Spain. Where they contracted the disease (and where they even came from) remained unknown, and by the second week after their arrival only four were still alive.
* Dutifully parodied by ''Webcomic/{{xkcd}}'' in the strip [[http://xkcd.com/734/ "Outbreak"]], in which patient zero is shot within five minutes and the threat ends before it goes anywhere.
-->The remaining ninety minutes of the movie will be a romantic comedy.
[[/folder]]

[[folder:Web Originals]]
* ''Website/AlternateHistoryDotCom'':
** Patient Zero for the Eurasian pandemic of SPID ([[CallARabbitASmeerp AIDS by another name]]) in ''Literature/ForAllTime'' was [[spoiler:a Soviet soldier who contracted it from a blood transfusion while in the Congo, then unwittingly spread it by donating his blood every three weeks]]. Thanks to constant warfare and the ineffencies of that country's blood donation system, by 2002 ''35%'' of the Eurasian continent has it.
** In ''1989: Wipe-out'', two lab workers become the index patients for an airborne strain of Ebola Zaire. Three weeks later, over 99 percent of humanity is dead.
[[/folder]]

[[folder:Web Videos]]
* ''WebVideo/EconomyWatch'': David was Patient Zero of the Economic Virus in Episode 11, "Night of The Economic Dead".
* ''WebVideo/SecretLifeSMP'': On Day 7, Gem's Day 7 secret task assigns her as this for an outbreak of the Boogeyman curse, i.e. the ZombieApocalypse, and instructs her to spread it until either the session ends, every non-Red Name is infected, or she drops to her final life and chooses to forfeit the task.
* ''WebVideo/SlimecicleCinematicUniverse'': In the credits of "We Spent 100 Days in a Hardcore Minecraft Apocalypse", [[spoiler:Tommy is explicitly referred to as this, and was ''indeed'' the Patient Zero for the zombie virus]].
[[/folder]]

[[folder:Western Animation]]
* Cinnamon Bun of ''WesternAnimation/AdventureTime'' becomes Patient Zero in the episode "[[Recap/AdventureTimeS3E13FromBadToWorse From Bad to Worse]]". Why? Because he ate a piece of zombie flesh. Did we mention Cinnamon Bun is a [[TooDumbToLive complete moron]]?
* An episode of ''WesternAnimation/CodenameKidsNextDoor'' has a little girl named "Patient C" play this. She's apparently supposed to be infected with cooties, with the (entirely male) science staff using Numbah Four as justification for her being infected. Numbah Four has extremely large, swollen lips after eating coconut logs even though he's violently allergic.
* In the ''WesternAnimation/FamilyGuy'' episode "[[Recap/FamilyGuyS9E4HalloweenOnSpoonerStreet Halloween on Spooner Street]]", Quagmire is shown to have contracted every STD known to man, which includes being patient zero for gonorrhea.
* In the ''WesternAnimation/{{Futurama}}'' episode "[[Recap/FuturamaS6E24ColdWarriors Cold Warriors]]", Fry is patient zero of the common cold which had been eradicated centuries ago. He carried the virus after being frozen for a thousand years spreading to the Planet Express crew and Manhattan.
* ''WesternAnimation/TheSimpsons'': In the "[[Recap/TheSimpsonsS21E4TreehouseOfHorrorXX Treehouse of Horror XX]]" segment "Don't Have a Cow, Mankind" (a parody of ''Film/TwentyEightDaysLater''), Patient Zero is Kent Brockman, who is reporting on Krusty Burger's new sandwich; Burger 2, which is made from cows that have been fed other cows before slaughter, and unfortunately turns anyone who eats it into a rage zombie. Brockman is the first person to try it, which leads to him becoming infected on camera, and attacking Krusty, with the entire town being overrun by rage zombies in less than a month, as the infection only takes a few seconds to set in.
* In ''WesternAnimation/TheSmurfs1981'', Lazy Smurf is the original carrier of the Purple Smurf virus that very nearly wipes out the Smurfs. In [[ComicBook/TheSmurfs the comic it was based on]] (itself old enough to be an UrExample of ZombieApocalypse), it's Grouchy Smurf who is Patient Zero of the Black Smurf virus, and it's given as an explanation for why he is so grouchy (he's the first to catch the virus and the last to be cured).
* ''WesternAnimation/SouthPark'':
** In "[[Recap/SouthParkS1E7Pinkeye Pinkeye]]", Kenny becomes a zombie and causes an undead outbreak. He gets killed, and the originally undead return to life. The boys are actually told to kill the original zombie, and not just kill random zombies. This news comes a little too late, as they had already killed half the town by this point.
** In "[[Recap/SouthParkS17E3WorldWarZimmerman World War Zimmerman]]", Cartman believes Token to be patient zero, but this is just Cartman's racism.
** "[[Recap/SouthParkThePandemicSpecial The Pandemic Special]]" shows Randy was the Patient Zero for the UsefulNotes/COVID19Pandemic after he had sex with a pangolin back during his [[Recap/SouthParkS23E2BandInChina trip to China in the previous season]].
* In Episode 5 of ''WesternAnimation/WhatIf2021'', "[[Recap/WhatIfS1E5WhatIfZombies What If... Zombies?!]]", Janet Van Dyne is revealed to be this. Hank Pym goes to the Quantum Realm to save her, just like in ''Film/AntManAndTheWasp'', but by the time he gets to her, she's already been infected. Once she and Hank return to Earth, they end up unleashing a ZombieApocalypse that even the Avengers couldn't stop from spreading.
[[/folder]]

[[folder:Real Life]]
* TyphoidMary, who caused many outbreaks of [[ExactlyWhatItSaysOnTheTin Typhoid Fever]].
* Although he was [[https://www.eurekalert.org/pub_releases/2016-10/uoc-nr102416.php eventually exonerated]] as being the true Patient Zero, [[http://en.wikipedia.org/wiki/Gaetan_Dugas Gaetan Dugas]] was widely reported as being Patient 0 of the HIV/AIDS epidemic, at least in the western world, especially after the book ''And the Band Played On'' was published and placed a large amount of blame on him for the virus' spread in North America. He was actually labeled as Patient ''O'', meaning "Out(side)-of-California" which was mistaken for a number due to a typographical error. The True Patient Zero, whose identity remains unknown (and will likely remain so) was from somewhere in Africa, most likely in the basin of the River Congo, where a mutation of a Simian Immunodeficiency Virus (SIV) from the white-collared monkey jumped the species barrier either when someone ate meat from an infected monkey or (more likely) when blood from an infected monkey found its way into a cut on a human (most likely while hunting or butchering a monkey for meat).
* Back in 1976 when the Ebola virus was first identified and named it was traced to Yambuku, a small village in Mongala District in Equateur Province in northern Democratic Republic of the Congo (previously Zaire). The virus was first identified in a blood sample from a Flemish nun. After the fact through testing it was discovered that an outbreak in Sudan several months previously could be traced to a storekeeper known as YG in a cotton factory in Nzara, so he is considered the Patient Zero of the virus since he's the first known individual to have been infected.
** Thomas Eric Duncan is considered the USA's patient zero for the 2014 USA Ebola outbreak.
** Teresa Romero, a Spanish nurse, contracted Ebola from a priest who was sent home from Liberia. That technically makes her "patient one" for Spain. Brother Miguel Pajares and Brother Manuel García Viejo were both technically patient zero for Spain[[note]]no one caught the Ebola virus from Miguel before he died and Teresa received the virus from Manuel[[/note]].
* It is believed that the patient zero for the modern Zika virus outbreak was probably someone who went from French Polynesia to Brazil before the 2014 FIFA World Cup. We still do not know and probably never will know this patient's identity. When the Zika virus was first isolated in 1947 it was found in a rhesus monkey in a forest near a town called Entebbe, Uganda, and the first human infections were identified in 1952 in Uganda and Nigeria.
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