What was Desmond's exact quote about almost being a doctor?
		
		
	 
"What do you know about sprains?""I was almost a doctor once."
"Small world."
		
 
		
	 
Thanks.  I have a feeling Desmond is some kind of medical/disease researcher.  The mainframes recording data.  The quarantine sign indicating the outside of the hatch.  The serum he injected into himself as some type of antibody/vaccine.
		
 
		
	 
I've been thinking about this, and I think you are right.Desmond is a medical researcher of some kind.
		
 
		
	 
No I haven't read any spoilers.The confusing thing about the guy living in the dome is that he clearly is not in direct physical contact with the outside world and has not been for at least 20 years.  The computer system is too old.  He's replaying old vinyl records repeatedly.  I'd date the technology in there to at least 1985.
But we saw him when he stepped out right at the end of the episode.  Not one hair in his flowing mane was gray.  Couldn't be older than his late 30s.  I highly doubt he is dying his hair.  So he was no older than a teenager when he first was there.
This brings up the possibility that a parent/mentor set up that lab, died or disappeared, leaving him in charge.