"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]