Back in the early '90s I used to own a pool hall. The constant interaction with the public made me an incubator for every germ that came into the room. I was sick constantly. Now, I probably wasn't the picture of healthy living at the time and even though I've never smoked, back then I second hand smoked more than anyone alive.
Flash forward a couple years and I don't think I got sick one time between 1996 and 2006. I was an accountant and stuck in an office and generally took a little better care of myself.
Now I have 2 kids and training and I'm back to catching everything that comes around. When you punish your body as much as I do all your energy goes to healing your joints and muscles. There's nothing to spare for your immune system. Last year I went and got a bird flu vaccine on the premise of a compromised immune system. I had to explain that I didn't have AIDS but that my body just doesn't have the energy to fight anything.
Right before the race in November I started getting sick and by the week after it I thought I was afraid that I was going to die. I had caught a pretty bad cold/flu and with my body being in the shape that it was it really knocked me for a loop. I read in an article by Chris Carmichael that the probiotics in yogurt help to fight off colds and flu. I've had a yogurt almost every day since then and I haven't been sick once this year.
Knock on wood.