I keep coming back to Susan Sontag's "Illness as Metaphor." It is so natural to experience illness or other suffering as punishment. The graver the illness, the greater the sin. My brother-in-law's mom on her deathbed shouted repeatedly "What have I DONE?!!"
But the alternative -- that suffering visits us at random, without regard to whether there is a symbol of our piety at the door frame, is both more likely true and still harder to comprehend.