Three days after his liberation, Elie Wiesel becomes very ill with food poisoning, hovering "between life and death." Why is this ironic?

To have survived all that he has survived - the death camps, the malnourishment, the horrible conditions, the death march, only to have his life threatened after he is liberated is certainly ironic.  The idea of hovering between life and death, as quoted, is also an ironic thought in that Elie has been there for years, under the Nazi regime in the concentration camps, and now finds himself near death from a relatively simple medical condition.

Add to this the idea that he went without food so often, and for so long - that malnourishment was one of his biggest threats in captivity - and yet in the end, food itself, consumed after liberation, nearly took his life.  There is a lot of irony in Elie Wiesel's story.