So do I. Half of my small office heads to Toronto in several weeks for a conference. I'm going to take almost all of my vacation time to avoid being here during the incubation period when they return. I have an asthmatic child at home and don't want to take any chances.
Twigs! You might want to print out the article on the New England Journal of Medicine's site linked here...
http://content.nejm.org/cgi/content/full/348/20/e6 and take it to your co-workers, expressing concern. Please note the sentence in the second paragraph indicating that people can be "infective" even though they are not showing any symptoms yet, but are still incubating the illness.