A man suddenly feels faint and lightheaded at home so his wife rushes him to the ER.  The doctor on duty gives him a thorough examination and seems quite concerned the entire time.  He looks the man up and down curiously  
 
DOCTOR: Have a seat in the waiting room and and have your wife come in.

the husband, clearly shaken, leaves and a moment later his wife apprehensively comes into the examining room and the doctor offers her a seat.

DOCTOR: Your husband has a very rare disease.  The only known cure is for you to have sex with him every night for the rest of his life.  If you do this he’ll live a long and happy life.  Do you know what I'm saying?

WIFE: Yes. Sure I do.  Thank you so much doctor. I understand.

DOCTOR: Good.  Now go take him home.

She stops and turns to the doctor.

WIFE: Can I ask you one question?

DOCTOR: Of course

WIFE:  Just out of curiosity, what if I don’t – have sex every night, I mean.

DOCTOR: He’ll be dead within a month

The wife nods her head solemnly and goes out to the empty waiting room.   She gives her husband a small hug without looking at him and without a word.  They just sit there in silence for what seems like forever until the husband can't stand it anymore.

HUSBAND: Did you talk to the doctor?

WIFE: Yes, I did.

HUSBAND: Well… what did he say?

His wife takes his hand, then gently strokes his hair, looks him in the eye

WIFE: You’re going to die