According to Leviticus 13:4, those suspected to have leprosy were to be quarantined.
Where were they quarantined?
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The Shadal states that he is quarantined in his own house.
More interestingly, however, he quotes the Rash as saying that the translation of that verse is not "the kohen quarantines the one with the blemish" but rather "the kohen closes the blemish" with a line drawn around it, in order to determine if it is growing.