Jacques’s death gets so much text time, we can be pretty sure it’s about a little more than a boy dying (not that a child dying is insignificant; we’re not cold-hearted, we promise). It doesn’t take much hemming and hawing to conclude that Jacques death is about the cold indifference of pestilence and the fact that everyone, child or adult, innocent or criminal, suffers just the same. On top of that, there’s a good deal of religious stuff going on here too. Most obvious is the image of Jacques laying flat "in a grotesque parody of crucifixion," but more subtle references include the fever’s advancing "three times," a number not insignificant in the story leading up to Christ’s death (Peter denies Christ three times and Jesus prays three times in the Garden of Gethsemane the night before his death, to name just two). If you’re interested in this sort of thing, check out Father Paneloux’s death for similar imagery.
The irony, of course, is that according to Christian beliefs, Jesus died for the sins of mankind. Jacques, on the other hand, dies for nothing at all. The religious imagery Camus uses here really drives home the notion of senseless and irrational suffering.