The Unselfish Gene

It's love and terrorism in the time of cholera. In the mid-21st century, a form of bird flu has killed billions and turned most of the rest into mindless, stumbling zombie-like invalids. The few humans who had immunity now face the threat of a comet on a collision course with Earth. Settlers from the Moon colony were spared the disease, but face their own threats to survival: radiation-induced mental illness, a limited gene pool and shrinking resources. The Moon settlers have launched a last-ditch mission to Earth to salvage human DNA and other crucial materials... before the comet strikes. The salvage crew find the biggest threat to the mission is neither the zombies or the comet, but insanity within their own ranks.