Elie's near-death experience after the camp's liberation is an example of situational irony. After losing his sister, mother, and father, after suffering beatings and malnourishment, after being hospitalized for a serious foot infection, and after enduring a overnight marathon in freezing conditions, Elie should be able to begin the emotional and physical recovery process. However, when he finally has his freedom--something that he survived for--he is unable to enjoy it because his physical and mental health are so dissipated that he is hospitalized and nearly dies. Elie's situation near the end of Night is not all that different from his father's, for his dad makes it through quite a bit of the horrific camp experience before succumbing to death. If he had been able to live a brief time more, then he would have most likely been able to get the medical treatment and freedom that he needed and longed for. Both Elie and his father experience the dark irony of being so close to freedom but not being able to enjoy it.
Wiesel wisely juxtaposes his illness at the end of Night with his spiritual death. When he sees himself in the mirror, he not only witnesses the physical changes wrought on him by the Holocaust; he also recognizes the empty, soulless eyes of one who has lost his faith. Thus, while he survives physically, Elie's spiritual being is a corpse to him--another example of irony.