Lepra: various etiologies from miasma to bacteriology and genetics.

Leprosy is a chronic infectious disease caused by a close relative of Mycobacterium tuberculosis: Mycobacterium leprae. There have been various beliefs in its etiology with two main concepts emerging: anticontagion and contagion. From ancient times through the early Middle Ages, the miasmatic theory of leprosy was the main anticontagion view.