An epidemiologist's view of leprosy.

While leprosy has been studied exhaustively by leprologists, it is only recently that persons in other disciplines have given this disease the attention it deserves. Various methods for its prevention and control are now being advocated and tested in the field, and it appears reasonable for an epidemiologist to review the bases of current theories and to examine the evidence for existing hypotheses. This has been done by a review of some of the more recent literature. The conclusion is reached that the anergic, or factor N, hypothesis that has been evolved to relate the lepromin test to the findings in clinical leprosy appears to be the most promising, and that, if this hypothesis can be substantiated, it is unlikely that BCG vaccination can be a very useful tool for prevention. Many possibilities exist for epidemiological and laboratory research into this disease, which in many ways appears to be unique.