You need to ingest the particles. So if you either wash your hands before you touch your nose, mouth or eyes OR don't touch your nose, mouth or eyes then you cannot catch it. Unless they vomit right in the room with you and then there would be airborne particles. You CANNOT catch anything, even the Norwalk virus, by just breathing near someone who is sick. So relax, don't touch your mucus membranes, and wash hands before you do.