cordon sanitaire

noun, plural cor·dons sa·ni·taires [French kawr-dawn sa-nee-ter] /French kɔr dɔ̃ sæ niˈtɛr/.

1. a line around a quarantined area guarded to prevent the spread of a disease by restricting passage into or out of the area.
2. a group of neighboring, generally neutral states forming a geographical barrier between two states having aggressive military or ideological aims against each other.

noun

1. a guarded line serving to cut off an infected area
2. a line of buffer states, esp when protecting a nation from infiltration or attack

n.

1. A barrier designed to prevent a disease or other undesirable condition from spreading.