Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 112

להיות המצורע ידוע לכל בדברים האמורים בו "בְּגָדָיו יִהְיוּ פְרֻמִים וְרֹאשׁוֹ יִהְיֶה פָרֻעַ וְעַל שָׂפָם יַעְטֶה וְטָמֵא טָמֵא יִקְרָא" (ויקרא יג, מה). וכן כל שאר הטמאים צריכין להודיע את עצמן.

For a person afflicted with tzara’at to make known his condition to all others, according to the instructions mentioned in [Leviticus 13:45]: "His garments shall be torn, his hair shall grow uncut, he shall cover his face to the lip, and he shall cry out: `Impure! Impure!"' Similarly, all others who are ritually impure must make known their condition.