"In the old testament part of the law involved keeping lepers separate from the main population. I always assumed this was because the disease was very contagious and God did not want it to spread. However i have since learned that leprosy is not very contagious at all and that one could live with a leper and not get leprosy. Since the spread of the disease was not an issue why would god still make them stay separate?

"I'd call this an apolegetics issue (albeit minor) because it plays a role in the continuity of the bible with history. If lepers were separated because of superstition or for no society benefiting purpose like they are in many other cultures then Gods law would seem petty(in this area) since he would have these people separated and potentially harmed for no good reason.

"Leprosy, Leper. Chronic infectious disease caused by Mycobacterium leprae, a bacterium similar to the tuberculosis bacillus. The disease is manifested by changes in the skin, mucous membranes, and peripheral nerves. In the skin there are often patches of depigmentation but rarely a total loss of pigment, so a pure white patch of skin is definitely not characteristic of leprosy. Loss of sensation to touch and temperature is frequently associated with the depigmented patches. Thickening of the skin and nodule formation cause the lionlike facial appearance commonly associated with leprosy. Peripheral nerve involvement may cause paralysis of a hand, leg, or face, or it may cause loss of sensation so complete that serious injury or ulceration to an extremity may occur without the afflicted person knowing it. The eyes, ears, and the nose are also frequently involved. An effective though prolonged treatment has been developed, and sometimes spontaneous arrest may occur. The disease is spread through prolonged contact with an individual having leprosy. Children are more susceptible than adults, but in any case the transmissibility is low. ...The early history of leprosy is shrouded in uncertainty. Possible references to leprosy have been cited in ancient Egyptian, Babylonian, and Indian writings, but authorities disagree whether the records refer to modern leprosy. This ambiguity in these early records is significant because it limits the help they might give toward our understanding of the meaning of “leprosy” in the OT.
In the Old Testament. Leviticus 13 and 14 contain the most details about what is called “leprosy” in the Scriptures. Careful study of the descriptions of the disease given in these passages strongly suggests that what we now diagnose leprosy is not intended. If a priest today used the criteria given in these verses, he would probably declare many leprosy patients unclean; but he would also pronounce unclean many individuals with a variety of other skin conditions. The disease we call leprosy does not fit the description given in Leviticus. The white hairs referred to so frequently in these verses are not typical of leprosy and may be found in many skin diseases. A white patch of skin is not characteristic of leprosy, nor is the scalp ordinarily affected. A 7- to 14-day period is usually inadequate to observe changes in the disease. If modern leprosy is being described in these verses, it seems strange that the more obvious characteristics of the disease are not mentioned. The bacillus of leprosy has defied attempts by bacteriologists to cultivate it, so leprosy of garments or houses is most unlikely to occur. Therefore the biblical leprosy is not synonymous with modern leprosy. The Hebrew word translated “leprosy” is derived from an Arabic word meaning to strike down or scourge; thus it could be a generic term for serious skin diseases or for signs of defilement on the surface of inanimate objects. ... Criteria are given in Leviticus 13:2–8 by which the priest would determine whether a given skin condition was to be regarded as leprosy. Different types of leprosy are described in Leviticus 13:9–59. An ulcer appearing with white skin and hairs was termed chronic leprosy, and the person was declared unclean but without the need of a quarantine period. Another type of leprosy, involving the entire skin, did not make the person unclean. Leprosy coming after the healing of a boil is described in verses 18–23, and after a burn in verses 24–28. In verses 29–39 the description given for leprosy of the scalp and beard is suggestive of a fungus infection. Leprosy in connection with baldness is described in verses 47–59. If “defiling disease” instead of “leprosy” were used in the translation of these verses, as suggested by an eminent leprologist, it would eliminate much confusion and probably convey the true meaning of the original word more accurately." [Freedman, D. N. (1996, c1992). The Anchor Bible Dictionary (4:277). New York: Doubleday.]


"The fourteen-day quarantine for suspected malignant saraat has been quite correctly regarded as much too short for clinical leprosy to develop. But it would have allowed certain differential diagnoses, such as scabies or ringworm, to be made. Thus the quarantine would have helped to safeguard the interests of priests and patients alike, since the diagnosis of leprosy even today can be difficult in the early stages of the disease. " [ISBE]