Sitting on a crowded bus a woman is talking loudly on a cellphone. She tells the person on the other end of the phone that she has a highly contagious airborne disease. Only one person looks up while listening. later after she exits the bus. No one talks about what was said, and in fact they happily go about their business. the person who looked up is the only one who covers her mouth. Why?
If you know the answer write a comment. I'll leave this up until my birthday or until someone answers it correctly.