[[caption-width-right:308:Healthcare Made Simple! Or not so much...]]

Parasitology is a medical thriller series by Mira Grant, (aka Creator/SeananMcGuire).

It is 2027. The hygiene hypothesis -- the idea that we have scrubbed our environment so much that we can't handle incursions by germs and parasites -- has found a solution. [=SymboGen=], the mega corp, has come up with a pill that contains the egg of a genetically engineered tapeworm called the Intestinal Bodyguard which regulates the body. Diabetic? The Intestinal Bodyguard will make sure you have enough insulin to never worry. Live in a third world country with no women's rights? The Intestinal Bodyguard will emit hormonal birth control. It's healthcare made simple. One pill, every two years -- never get sick, never have to remember to take meds for your issues.

The story follows Sally Mitchell, who -- six years before the narrative begins -- had a seizure behind the wheel of her car, resulting in a car accident that left her gravely injured and in a coma from which no one expected her to wake. As her family discussed whether to unplug her life support, Sally awoke. The family was thrilled to have Sally back. [=SymboGen=] was delighted to take the credit and foot the bills for Sally's rehabilitative therapy (so they could study her). Sally, for her part, wasn't sure how to feel about ''any'' of this, as she [[BlankSlate couldn't even remember how to speak]].

Things take a sharp turn into the weird and terrifying as people begin coming down with a strange sickness. Most people call it sleeping sickness -- but it looks frighteningly similar to becoming a zombie.

Sally and her boyfriend Nathan begin to wonder what's going on, and whether [=SymboGen=] has been entirely honest about their product.

The series consists of ''Parasite'', ''Symbiont'', and ''Chimera''.


!!This series contains examples of the following tropes:

* ActionSurvivor: Both Sally and Nathan.
* AffablyEvil: Dr. Banks.
* AirVentPassageway: Sally tries escaping a mall this way in ''Symbiont'', only to find Ronnie waiting for her at the end; once he saw that she'd entered the vent, he was able to casually stroll over to the exit grating while she slowly crawled her way through the duct.
* AllThereInTheManual: There's an in-character {{Twitter}} account for [=SymboGen=].
* AndThenJohnWasAZombie: [[spoiler:The end of the first book reveals Sally's parasitic implant is in her brain, meaning she's just like Adam and Tansy -- a sentient tapeworm inhabiting a human body]].
* AxCrazy: Tansy.
* BioPunk
* BiTheWay: Randy Englishman Sherman dates both sexes and is open about it so there's no concern of cheating.
* BigBadFriend: [[spoiler:Sherman, one of the [=SymboGen=] scientists who is friendly with Sally and who gets taken away after Chave's Intestinal Bodyguard takes over, turns out to have been in on the scheme the whole time, and another one of Shanti's experiments who betrayed her]].
* CallingTheOldManOut: It takes a long grounding period and a very ill-advised ruse by her father to elicit more information out of her, but Sally eventually gathers the courage to tell her parents off and make them revoke their custodianship of her.
* CorruptCorporateExecutive: Banks.
* DarkActionGirl: Disconcertingly combined with GenkiGirl in the person of Tansy.
* DrivenToSuicide: [[spoiler:Richard Jablonsky, one of the co-founders of [=SymboGen=] is revealed to have killed himself when he realized how bad things were getting, and couldn't convince Banks to listen]].
* DysfunctionalFamily: Played with. Sally after the accident has an entirely different personality than Sally before the accident. Pre-accident Sally was a bit of a hellion and contrary for the sake of being contrary. Sal is compassionate and empathetic, willing to talk to her family. Her family is torn between missing the old Sally and appreciating the new Sally -- to a point.
** Her parents' reaction to Sally going off the grid for a day is explained in-universe, but also called out as being ''completely out of order''.
* EvilDetectingDog: [[spoiler:Animals such as dogs and cats can tell when a person's Intestinal Bodyguard is taking over, due to the sudden change in hormones. However, they react normally to those who have already been taken over, such as Tansy and Sally]].
* FaceHeelTurn: [[spoiler:Sherman is revealed to be one of Dr. Cale's sentient tapeworms who defected to Banks's side]].
* FakingTheDead: [[spoiler: Dr. Shanti Cale dropped off the radar right around the time the Intestinal Bodyguard went public. She is also Nathan's MissingMom]].
** [[spoiler:After Sherman is taken away by [=SymboGen=] security, Sally is told that he had been 'infected' by Chave. This later turns out to be not the case]].
* ForScience: Kale's prime motivation for working for Banks.
* {{Foreshadowing}}: In his first appearance, Sherman refers to Sally's boyfriend as a 'parasite pasher', i.e. someone who kisses tapeworms. [[spoiler:Sally later finds out she's a tapeworm]].
* HideYourGays: Subverted. As with Grant's other works, her same sex relationships are treated as no different than heterosexual relationships.
* InfantImmortality: Subverted - one of the first sleepwalking victims that Sally encounters is a little girl.
* IronicNurseryTune: ''Don't Go Out Alone'', verses of which are scattered across the gaps between chapters. Technically, not a tune, but just as creepy as most instances of this trope.
** More ironically, it actually has a tune- it is uncertain which version came first, but the author did a [[http://seananmcguire.com/songbook.php?id=69 filk]] about Silent Hill. Presently there don't seem to be plans to record ''Don't Go Out Alone'' (probably because then she'd have to write the whole thing).
* LiteraryAllusionTitle: The interludes are named after books from Literature/TheBible (Genesis, Exodus, Numbers, Judges).
* LEGOGenetics: The ''Diphyllobothrium symbogenesis'' Intestinal Bodyguard parasite is made from a mishmash of human and parasite DNA. Because of the intertwining of DNA from disparate species, taking antiparasitics might have an adverse effect on their host's DNA as well. It's later revealed that [=SymboGen=]'s parasite includes DNA from another source: [[spoiler:''Toxoplasma gondii'', a parasite which can affect its host's behavior]].
* MadScientist: Dr. Shanti Cale.
* MissingMom: Nathan's mother died abruptly on him at a young age. They were very close, so he took it hard and required years of therapy. [[spoiler:She turns out to not have died after all, having had her death faked by [=SymboGen=] so her family would remain safe in case things went wrong. Nathan takes it all in stride, having figured out who Shanti Cale was long before the events of the book, though he's not exactly happy about it]].
* MoralityKitchenSink: Sally and Nathan are the good, Symbogen the bad, as is [[spoiler: Sherman]] with [[spoiler: Shanti Cale]] and Sally's father somewhere in the middle.
* NotUsingTheZWord: So far the possessed are being referred to as "sleepwalkers".
* ParasiteZombie: The sleepwalkers.
* PuppeteerParasite: [[spoiler:The Intestinal Bodyguards are becoming more aware and taking control of their hosts, thanks to the little extras that the people working on them threw in]].
* TheReveal: Book 1 ends with [[spoiler: Sally discovering she's one of the tapeworms]].
* ShownTheirWork: As if ''Literature/{{Newsflesh}}''[='=]s Kellis-Amberlee virus wasn't convincing enough, in this series, Seanan [=McGuire=] explores yet another plausible way for a ZombieApocalypse to come to pass. Think ''Toxoplasma gondii'' and its espoused mind-control abilities are just another horrific sci-fi fabrication? [[http://www.strange-loops.com/blog/?p=59 Think again.]]
* SpockSpeak: Having to learn English all over again leaves Sal a bit overly formal in her speech patterns.
* TechnicallyLivingZombie: The sleepwalkers.
* ThatManIsDead: Without any memories from before the accident, Sal is insistent that she be considered a separate person from her former self, which is why she doesn't go by Sally anymore.
* TomatoInTheMirror: [[spoiler:Post-crash Sally turns out to be her tapeworm, who took over Sally's brain in response to her body shutting down after her car crash. She works this out after meeting Adam and Tansy, but faints from the shock and forgets until the end of the book]].
* TwentyMinutesIntoTheFuture: Starts in the year 2027.
* TheUntwist: [[spoiler:Many people called Sal being a tapeworm as soon as their abilities were revealed. In fact, Sal herself realizes it at the same time but has a mental break over it, and the rest of the book is her struggling to not remember it.]]
* YouShallNotPass: [[spoiler:Tansy pulls this on a mob of sleepwalkers in order for Sally to get away. Nathan isn't sure if she survived or not, but Dr. Cale claims this isn't the first time it's happened]].
* ZombieApocalypse: Is headed in this direction by the end of the first book.