I hear ya. I've been battling a combination of sinus/allergy issues since Thanksgiving. Just can't seem to kick whatever is kicking me!
I agree though, many times, when a co-worker comes in, it just ends up spreading around and also takes longer for the orginially infected to get better. When my family had a business, and I was a manager, I would tell my employees if you have a fever, are coughing non stop, or your ahem boogers are abnormal then I don't want to see you at work. I'm sure they took advantage of it once in their lives, but it made the workspace more comfortable.