What word or phrase does your mother always say?
late 14c., from Old French contagion, from Latin contagionem (nominative contagio) "a touching, contact, contagion," related to contingere "touch closely" (see contact (n.)).
contagion con·ta·gion (kən-tā'jən)n.
Disease transmission by direct or indirect contact.
A disease that is or may be transmitted by direct or indirect contact; a contagious disease.
The transmission of an infectious disease resulting from direct or indirect contact between individuals or animals.
A disease that is transmitted in this way.
The agent that causes a contagious disease, such as a bacterium or a virus.