My younger son has H1N1 and, so far at least, I think all this drama about it is hype. Perhaps we just caught it early or he got a light case but so far the worst thing is the coughing. I've had more debilitating head colds. Just my two cents worth.
We are also teaching kids to cough/sneeze in their elbows. They remember to do that but they still put their fingers in their mouths or noses. That's what I'm working on in my classroom mostly now.
I think the suggestion to simply say, "I'm being very careful of germs during flu season" would be all you need to say.