Parasite

A decade in the future, humanity thrives in the absence of sickness and disease.

We owe our good health to a humble parasite — a genetically engineered tapeworm developed by the pioneering SymboGen Corporation. When implanted, the Intestinal Bodyguard worm protects us from illness, boosts our immune system — even secretes designer drugs. It’s been successful beyond the scientists’ wildest dreams. Now, years on, almost every human being has a SymboGen tapeworm living within them.

But these parasites are getting restless. They want their own lives . . . and will do anything to get them.
Parasitology
Parasite
Symbiont
Chimera

For more from Mira Grant, check out:

Newsflesh
Feed
Deadline
Blackout

Newsflesh Short Fiction (e-only novellas)
Apocalypse Scenario #683: The Box
Countdown
San Diego 2014: The Last Stand of the California Browncoats
How Green This Land, How Blue This Sea
The Day the Dead Came to Show and Tell
Please Do Not Taunt the Octopus