Sin as a Sickness

I love C.S. Lewis' use of analogies. He uses them to explain his statements, but also identifies when they fall short, the places where the two situations are not analogous. In the chapter on God's love, Lewis has to use different aspects of four analogies to attempt to explain God's love for His creatures.
I can't remember when it came up, maybe in the reading, maybe in class, maybe in something totally unrelated, but I've been thinking about sickness as an analogy for sin.
On the one hand, viewing sin as a sickness allows us to see the action as just a symptom of a much deeper problem. Popping cough drops like candy might keep everyone else from hearing about your illness, but it does nothing to cure the cold itself. Curing the outward expression of an inner struggle is futile, the sickness just reasserts itself, in different ways.
Sometimes, an analogy helps me to understand something in the ways it fails to fully explain the concept. 1 John 1:9 tells us that, "If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness." Confessing that I have a cold is unlikely to have any affect on the cold, while a pennant confession to God brings his forgiveness.