It's polite to sneeze into a tissue or your elbow.
Mark is on a plane, and he has a slight cold.
Mark needs to sneeze.
Mark gets out a tissue that he brought with him and proceeds to sneeze into it.
Mark sneezes without covering his mouth while on the plane.
The people on the plane feel fear hearing him sneeze but then feel relieved seeing that he sneezed into a tissue.
The people on the plane start becoming fearful that they might get the coronavirus.