- last post: 01.01.0001 12:00 AM PDT
Sarge has this thing called Boren's Syndrome which he got from using plasma grenades improperly; it affects your nervous system.
It's because of this syndrome that the Flood can't take him as a host; they need the nervous system to sustain themselves, but since Sarge's is all messed up they can't do a thing.
Anyways, he was able to escape the Forerunner complex, call for a Pelican to evac him, then was able to escape Halo.
And there is no real answer to how he got from hugging an Elite to escaping Halo. My guess is that Bungie didn't expect him to be such a popular character and killed him off too soon.