I have had people to take a few steps away from me as soon as I said "I have CF". I usually say right after that you cant catch it (unless i want them to go away...j/k). You have to be born with it. Your safe. And tell them the basics (effects ur lungs and other organs, specially since my coughing is what scares ppl) about it and see if they have any questions. For people that still dont believe me, I have told people that it is kinda like asthma (for those who have asthma, please do not get upset, most people know what asthma is and asthma is more common that cf) in the fact that it effects my lungs but you cant catch it. I later add about digestive issues, specially if they see me eat and take meds.