Nerve parasite in short story

Question

The short story I refer to began with a cave in, collapse, or other type of mass accident where only one person lived. The parasite jumped from its dying host into that last living person. -- Im a little unclear of detail beyond this point, but the new host was rescued. Turns out he was already suffering a terminal disease. He did battle with the parasite to the point of ending his life in isolation so it would have nowhere to go. ---- I sure would like to read it again!

A little more detail that might help: The guy was a Dr, I think. Anyway he had good physiological knowledge. He was able use this to surgically thwart the parasite trying to control his body as he took his life. The mental/physical battle was short in duration but VERY well developed in the story. I read it about 12 yrs ago. I thought it was a Stephen King, but havent been able to [re] find it.

Answer 1

This is "The Autopsy" by Michael Shea.

The alien parasite is found in the body of a miner who died in a mine collapse by the doctor doing the autopsy.

As you say, the doctor has cancer, and deals with the parasite by allowing it to infect him, and then committing suicide.

The story can be read in its entirety at the Internet Archive.

This story was also the unaccepted answer to this old question: Story identification: medical examiner vs. alien parasite