I think when Barb was teaching my immune system was getting toughened up: all the germs from all the kids would ride into our house on Barb, hop on me, and give me a sound workout. Now there's a double whammy: Barb's tutoring job only exposes her to a few kids a week, and since I'm working with such a small group (typically by myself) my immune system is like a newborn baby.
My evidence? I'm getting over my second bout of sickness this season, and I rarely get sick even once. Slim, to me sure, but still enough for a blog entry.