system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If a disease needs a host to live, then potentially kills the host will it eventually become extinct once everyone is either immune or dead? What is the benefit of killing the host?
gpt
Most diseases keep the host alive long enough to multiply and spread.  You’ll often hear of diseases that are communicable for several days before the host shows any symptoms.

Continuation of the genetic material is the only pressure or driver, diseases don’t “plan” to kill or sustain the host.

You’re right that if a disease kills the host very quickly, then the outbreak will “flame out” on its own.

At the other end, if you think of colds, they don’t kill very many people at all and can keep cycling through a population, pretty much indefinitely.

So, there is no “benefit” because earlier generations of disease are not sentient.  They either spread well due to delayed host death or they spread poorly because they kill the host early.