Actually, I was thinking of King's first reference to "Captain Trips", in the short-story "Night Surf" from the awesome "Night Shift" collection of King short stories.
Night Surf
As that link explains, "Night Surf" was written prior to "The Stand"...
//sorry - King buff here.
Did you have a chance to read the unabridged version of The Stand? The original release had 400 pages of it redacted. The subsequent release after the movie included the extra 400 pages.