Clay's Ark by Octavia Butler

Clay's Ark (c. 1984) is one of Butler's Patternist novels. Like Mind of My Mind, it is chronologically one of the first of the Patternist novels, though written later sequentially. Clay's Ark tells the story of the origin of the Clayarks (mutant humans who are enemies of the Patternists in Patternmaster.)

Clay's Ark is a spaceship that has crash-landed on earth. All of the astronauts from the ship are killed on impact or have died from a virus/micro-organism picked up off-world, except one. One astronaut, Eli, has survived. The micro-organisms he picked up off-world are controlling his behavior in several ways: he is compelled to pass on the disease, his dietary needs have changed, he is compelled to mate with ovulating females, and his offspring will be mutants.

Eli crash-landed in a remote, desert area where he stumbled onto a farm and infected the people living there. They are trying to remain self-sufficient and avoid contaminating others, but they occasionally go on "raids" to find mates for the remaining residents of the farm. In one such raid, they encounter a father (Blake Maslin) and his two daughters (Keira and Rane.) Blake is a doctor, Keira is dying of untreatable leukemia, and the Rane is a healthy and nubile female.

Clay's Ark tells the story of the struggle between the farm family and the Maslin family. The farm family believes that they must contain the Maslins, who have surely been infected. The Maslins believe they must escape--especially Blake, who wants to notify the authorities about the virus/micro-organism, before it becomes a pandemic. Meanwhile, life in America has degenerated such that driving on the highway is unsafe. People with money live in walled compounds. People on the road are likely to be either roving bands of criminals or their victims.

Along with Mind of My Mind, Clay's Ark provides the backstory for Patternmaster. The mutant offspring of people infected with the off-world virus/micro-organism are the Clayarks.