History Main / TyphoidMary

* A significant percentage of people who who catch [[UsefulNotes/COVID19Pandemic COVID-19]] show few or even no symptoms. Even those who do eventually show severe symptoms will have had a lengthy period of asymptomatic contagion before then. All this leads to a disease that is spread mostly by people who, much like the TropeNamer, feel completely healthy and have no idea they've even been infected -- thus the importance of ''universal'' use of precautions such as mask-wearing and social distancing.

* A significant percentage of people who who catch [[UsefulNotes/COVID19Pandemic COVID-19]] show few or even no symptoms. Even those who do eventually show severe symptoms will have had a lengthy period of asymptomatic contagion before then. All this leads to a disease that is spread mostly by people who, much like the TropeNamer, feel completely healthy and have no idea they've even been infected.

* Children who catch [[UsefulNotes/COVID19Pandemic COVID-19]], as a general rule, show little to no symptoms. However, the disease becomes more likely to be serious when people grow older and/or have other health issues, so a seemingly healthy child can transmit the disease to a person who is more vulnerable to it.
** This is, in fact, true of the population in general, which is what makes COVID-19 so insidious and dangerous: some ''adults'' may be entirely asymptomatic (much like the TropeNamer), and can therefore spread it like wildfire without ever knowing they had unless precautions are taken when out in public, such as social distancing and covering the face.

The Typhoid Mary is a character who carries an infectious disease but doesn't suffer any visible symptoms -- in some cases she may actually be immune to it herself -- and spreads the disease to everyone she encounters.

In ZombieApocalypse works, there may be some overlap with the ZombieInfectee, depending on [[OurZombiesAreDifferent how the infection spreads]]. In most cases, however, the Zombie Infectee doesn't pose a danger of infecting others until he actually dies and become a zombie himself. The Typhoid Mary, on the other hand, is highly contagious from the first moment of her infection.

The TropeNamer is the RealLife example of Mary Mallon, the original "[[http://en.wikipedia.org/wiki/Typhoid_Mary Typhoid Mary]]" who spread typhoid fever to at least 53 other people while refusing to believe she carried the disease at all, because she never became sick from it herself. In biology/epidemiology, this is known as an "asymptomatic carrier" (i.e. carries the disease but shows no symptoms of it).

* In the second episode of ''Anime/{{Memories}}'', a man takes an experimental drug that causes anyone near him to die instantly. He never realizes he's dangerous (and doesn't realize that people are dying instead of just randomly going unconscious), and seems quite upset that everybody's trying to kill him.

* Lenie Clark of Peter Watts' ''Literature/RiftersTrilogy'' series carries βehemoth back to the surface world. However she isn't a proper example, since she spreads it deliberately.

* ''Flight from Tomorrow'', by Creator/HBeamPiper. A future dictator escapes a revolution with a time machine to the twentieth century where he plans to be a ConquerorFromTheFuture. However he turns out to be a WalkingWasteland because future mankind has become acclimatized to high levels of radiation after a series of atomic wars. The military track him and carpetbomb the valley he's in, then fill it with concrete from one mountainside to the next.
* ''Naples '44'', by Norman Lewis, details a plan by the Allies to send prostitutes behind German lines who were infected with severe cases of syphilis. Venereal disease had infected the Allied armies in Italy but not the German military, who ran their own brothels. Unfortunately the mission was cancelled and the women were released [[WhatAnIdiot so they could continue to infect Allied soldiers]].

** In episode "Jump The Shark" is about a biological terrorism plot based on sending out two Typhoid Maries. (Unusually for the trope, they are both fully aware and willing participants).

* On a wall in ''VideoGame/Left4Dead2'', some wall graffiti purports that some people are carriers of the zombie infection. It's loosely implied that the survivors might be carriers, not [[TheImmune immune]], as they had assume. This is confirmed in the comics for "The Sacrifice": the original ''VideoGame/Left4Dead'' survivors learn that they've been spreading the infection across the country and may have inadvertently doomed everyone who helped them in the previous campaigns. They then decide the only responsible way to save themselves is [[TheAloner reach an isolated island and live off the land]].

* ''VideoGame/TheElderScrollsIIIMorrowind'': One Tribunal Temple quest has you deal with a woman blessed by the [[PhysicalGod Tribunal]] who has caught the [[BodyHorror Corprus disease]]. She doesn't believe you because her "blessed" state means she isn't showing any symptoms. However, she can still spread the disease to others. You need to convince her to leave for the Corprusarium, or kill her.
* During the Mogloween 2011 event in ''VideoGame/{{DragonFable}}'', TheHero meets a little boy named Andy. Poor Andy is the only person who managed to escape from a Zardbie outbreak, but not unscathed. For some reason the bite he suffered hasn't mutated him into a Zardbie, but anyone who kisses him (happens twice because girls find him too adorable) or anyone he bites (such as a Gorillaphant) becomes a Zardbie. [[spoiler:A bad situation becomes worse when one of the people Andy unwittingly mutates is needed to make the Zardbie cure...]]

** In the same route, we also learn that [[spoiler: Ryouta, who already had a slightly weak immune system and weak stomach, got unknowingly experiemented on by Shuu, to make him a good carrier for the virus. He eventually implanted Nageki's liver into Ryouta, having him turn into his next Typhoid Mary]].

* The TropeNamer: Mary Mallon was a woman who worked as a chef in New York in the early 20[[superscript:th]] century. Everywhere she worked, her employers and the other household staff would all fall ill with typhoid fever, after which she would leave and find new employment. She was ultimately caught in 1907 and forcibly quarantined, given the nickname "Typhoid Mary" by the ''Journal of the American Medical Association'', and revealed that she did not wash her hands before cooking. She was given the option to have her gallbladder removed, or she would have to agree to never become a cook again. She was released 3 years later and forbidden from cooking. She changed her name and went right back at it, leaving a swath of typhoid fever infections in her wake. She was arrested again in 1915, and remained in quarantine until she died 23 years later in 1938. Autopsies showed her gallblader was full of live typhoid bacteria. Her treatment in quarantine was unusual in that other repeat offenders, including other food handlers and people who had more outbreaks to their name than her, got off with nary a reprimand and a promise not to do it again; the government threw the book at her because she explicitly ''refused to stop working as a cook'', backing them into a corner.
* This is one of the more serious problems faced by health workers trying to contain the 2014 Ebola virus epidemic. In the early stages the symptoms are so minor as to be barely distinguishable from the common cold, making ''every'' victim an asymptomatic carrier for the first couple of days. Most diseases eventually evolve to a point where they have a long period of little or no symptoms, as obvious symptoms and/or early death of the infected hinder the transmittal of the disease.
* Men with many [=STDs=] and bladder infections. As of yet, there is no method for detecting HPV (the virus that causes cervical cancer) in men. About 80% of the adult population are thought to be infected, although that may have changed due to the vaccination. Gonorrhea may not cause any symptoms at all in men, but can cause infertility in women (and, we now know, in men as well), and babies born to infected women can become blind from infection to the eyes, if left untreated. Even women tend to be asymptomatic more often than not. While men are more likely (although not guaranteed) to have a pus-like urethral discharge with chlamydia and gonorrhea that causes itching and burning, women may not know they have it (or had it) until they go for a routine OB/GYN exam or seek treatment for infertility, as they are less likely to have the "classic" symptoms associated with those diseases. And there are couples who have been bouncing ''Trichomonas'' back and forth for ''decades'', without even realizing it. This is why it's important to practice safe sex: limit the number of partners you have, use a fresh condom every time (and use it ''correctly''), wash "down there" before and after sex, and get tested (and if necessary treated) for [=STIs=] before having sex with a new partner.

* Many animals can be vectors for illnesses which do not affect them, but can be deadly for other species, such as humans. Bats in particular tend to be a common vector for serious infectious viruses like ebola, rabies, and SARS because they have extremely effective immune systems that minimize inflammatory symptoms at all times, but this in turn causes viruses within them to adapt much quicker to keep up, effectively causing bats to become a petri-dish of super-viruses.

[[folder:Anime and Manga]]

* Invoked in one episode of ''Series/MurderSheWrote'', in which a character named Ellen wryly refers to herself as "the Typhoid Mary of murder" - she herself is not murdered, but people around her are, and Ellen has a tendency to be accused of involvement even though she's completely innocent. Jessica, amused, tells Ellen that she can't be "the Typhoid Mary of murder" because that's Jessica's title.

[[folder:Theater]]

* The TropeNamer: Mary Mallon was a woman who worked as a chef in New York in the early 20th century. Everywhere she worked, her employers and the other household staff would all fall ill with typhoid fever, after which she would leave and find new employment. She was ultimately caught in 1907 and forcibly quarantined, given the nickname "Typhoid Mary" by the ''Journal of the American Medical Association'', and revealed that she did not wash her hands before cooking. She was given the option to have her gallbladder removed, or she would have to agree to never become a cook again. She was released 3 years later and forbidden from cooking. She changed her name and went right back at it, leaving a swath of typhoid fever infections in her wake. She was arrested again in 1915, and remained in quarantine until she died 23 years later in 1938. Autopsies showed her gallblader was full of live typhoid bacteria. Her treatment in quarantine was unusual in that other repeat offenders, including other food handlers and people who had more outbreaks to their name than her, got off with nary a reprimand and a promise not to do it again; the government threw the book at her because she explicitly ''refused to stop working as a cook'', backing them into a corner.

* Men with many [=STDs=] and bladder infections. As of yet, there is no method for detecting HPV (the virus that causes cervical cancer) in men. About 80% of the adult population are thought to be infected, although that may have changed due to the vaccination. Gonorrhea may not cause any symptoms at all in men, but can cause infertility in women (and, we now know, in men as well), and babies born to infected women can become blind from infection to the eyes, if left untreated.
** Even women tend to be asymptomatic more often than not. While men are more likely (although not guaranteed) to have a pus-like urethral discharge with chlamydia and gonorrhea that causes itching and burning, women may not know they have it (or had it) until they go for a routine OB/GYN exam or seek treatment for infertility, as they are less likely to have the "classic" symptoms associated with those diseases. And there are couples who have been bouncing ''Trichomonas'' back and forth for ''decades'', without even realizing it. This is why it's important to practice safe sex: limit the number of partners you have, use a fresh condom every time (and use it ''correctly''), wash "down there" before and after sex, and get tested (and if necessary treated) for [=STIs=] before having sex with a new partner.
* Children who catch [[UsefulNotes/CoronavirusDisease2019Pandemic COVID-19]], as a general rule, show little to no symptoms. However, the disease becomes more likely to be serious when people grow older and/or have other health issues, so a seemingly healthy child can transmit the disease to a person who is more vulnerable to it.

* In ''VideoGame/MetalGearSolid'', [[spoiler: Solid Snake was unknowingly infected with FOXDIE to kill the members of FOXHOUND and the [=ArmsTech=] President Kenneth Baker.]]
** This became a plot point in ''VideoGame/MetalGearSolid4GunsOfThePatriots'' when [[spoiler:Snake's accelerated aging and the age of the virus itself causes it to mutate; given a few more months, FOXDIE would have stopped caring whether its targets matched its targeting parameters, and Snake would have become a one-man plague. He was then infected with a second strain of the FOXDIE virus which helped cancel out the old virus and would not have enough time in Snake's body to mutate itself, as Snake was estimated to have one year left at most.]]

* Creator/PatrickDempsey's character in ''Film/{{Outbreak}}'' unwittingly infects a plane-load of people he's travelling with after he catches the virus from a monkey.

* Children who catch Covid-19, as a general rule, show little to no symptoms. However, the disease becomes more likely to be serious when people grow older and/or have other health issues, so a seemingly healthy child can transmit the disease to a person who is more vulnerable to it.

The TropeNamer is the RealLife example of Mary Mallon, the original "[[http://en.wikipedia.org/wiki/Typhoid_Mary Typhoid Mary]]" who spread typhoid fever to at least 53 other people while refusing to believe she carried the disease at all, because she never became sick from it herself. In biology/epidemiology this is known as an "asymptomatic carrier" (i.e. carries the disease but shows no symptoms of it).

* ''Literature/WorldWarZ'' had carriers' organs being harvested and sold on the black market, spreading the infection across the world.

* Children who catch Covid-19, as a general rule, show little to no symptoms. However, the disease becomes more likely to be serious as people grow older and/have other health issues, so a seemingly healthy child can transmit the disease to a person who is more vulnerable to it.

* In an episode of ''Series/{{ER}}'', one of the doctors spread a staph infection by not washing his hands adequately between patient visits.

* The TropeNamer: Mary Mallon was a woman who worked as a chef in New York in the early 20th century. Everywhere she worked, her employers and the other household staff would all fall ill with typhoid fever, after which she would leave and find new employment. She was ultimately caught in 1907 and forcibly quarantined, given the nickname "Typhoid Mary" by the ''Journal of the American Medical Association'', and revealed that she did not wash her hands before cooking. She was given the option to have her gallbladder removed, or she would have to agree to never become a cook again. She was released 3 years later and forbidden from cooking. She changed her name and went right back at it, leaving a swath of typhoid fever infections in her wake. She was arrested again in 1915, and remained in quarantine until she died 23 years later in 1938. Autopsies showed her gallblader was full of live typhoid bacteria. Her treatment in quarantine was unusual in that other repeat offenders, including other food handlers and people who had more outbreaks to their name than her, got off with nary a reprimand and a promise not to do it again.

* Younger children that catch Covid-19, as a general rule, show little to no symptoms. However, the disease becomes more likely to be serious as people grow older and/have other health issues, so a seemingly healthy child can transmit the disease to a person who is more vulnerable to it.

[[folder:Anime & Manga]]

* One season one episode of ''Series/MissionImpossible'' had a village full of people who were being trained by an East Bloc government to perfectly blend in with western society. The people all believed that they were being trained as deep-cover spies. In truth, their handlers planned to infect them all with the plague before shipping them out to their assignments.

* In ''Series/StargateSG1'', before the Ori gain the ability to attack Earth directly, they try infecting an SG team with a virus. When the team returns to Earth, they bring the disease back with them.

* ''Webcomic/WildeLife'': [[This is why [[OurWerebeastsAreDifferent animal people]] aren't supposed to eat humans--normal people can be carriers for "the Madness," a supernatural ailment that drives animal people insane and then [[WasOnceAMan turns them into monsters]]]].

* ''Webcomic/WildeLife'': There is a disease that can affect animal people (e.g. humans that can change into an animal form), that oridinary humans can carry without being affected by it. This makes it a very bad idea for animal people to actually bite an ordinary human.