Jamieson, Fausset and Brown on Leviticus 13:38-39

38-39. If a man ... or a woman have in the skin of their flesh bright spots--This modification of the leprosy is distinguished by a dull white color, and it is entirely a cutaneous disorder, never injuring the constitution. It is described as not penetrating below the skin of the flesh and as not rendering necessary an exclusion from society. It is evident, then, that this common form of leprosy is not contagious; otherwise Moses would have prescribed as strict a quarantine in this as in the other cases. And hereby we see the great superiority of the Mosaic law (which so accurately distinguished the characteristics of the leprosy and preserved to society the services of those who were laboring under the uncontagious forms of the disease) over the customs and regulations of Eastern countries in the present day, where all lepers are indiscriminately proscribed and are avoided as unfit for free intercourse with their fellow men.