Story about an adaptive, intelligent parasite "defeated" by humans

Question

Several years ago I read the plot synopsis on Wikipedia (bad form, I know) for a sci-fi story with an intelligent parasite that infected humans. The parasite adapted to all attempts to defeat or drive it out (e.g., by growing a hard exoskeleton on the affected person). The plot twist was that the parasite was conscious, and I believe the end of the book involved a woman "saving" her husband from the parasite by telling it that she would find it a new host if it would spare her husband.

Sorry for the kind of incoherent summary, it's been a long time since I read it.

For years I labored under the assumption that this story was Jeff Vandermeer's Annihilation, but I recently read Annihilation and it definitely isn't.

Answer 1

Is there any chance that it's Prey, by Michael Crichton? It's not a perfect match, but there are some similarities:

• The novel is about self-replicating nanobots that start as mindless swarms but evolve to take over human hosts.

• By the end of the novel, they are shown to have a form of intelligence.

• It is revealed that the protagonist's wife had been infected for some time.

• In the climactic scene, the wife is briefly freed from the parasite and tells her husband to escape and save their children while she uses the opportunity to destroy the facility they're in.

Answer 2

Could this be The Puppet Masters by Robert A. Heinlein? Since you remember it from a Wikipedia page rather than the book itself, I'll quote the first paragraph of the plot section:

In the summer of 2007, Earth is under clandestine attack. Slug-like creatures, arriving in flying saucers, are attaching themselves to people's backs, taking control of their victims' nervous systems, and manipulating those people as puppets. The Old Man, the head of a clandestine national security agency called the Section, goes to Des Moines, Iowa, with Sam and Mary, two of his best agents, to investigate a flying saucer report, but much more seriously the ominous disappearance of the six agents sent previously. They discover that "the slugs" are steadily taking over Des Moines, but they cannot convince the US president to declare an emergency.