The Leper's bell

… habebit vestimenta dissuta caput nudumos vesta contectum contaminatum ac sordidum se clamabit,

omnu tempore quo leprosus est et immundus solus extra castra.

And the leper in whom the plague is, his clothes shall be rent, and his head bare, and he shall put a covering upon his upper lip, and shall cry, Unclean, unclean.

As long as he has the infection he remains unclean. He must live alone: he must live outside the city.

Leviticus 13: 45-6