Who is commonly affected

Nearly 95 to 98% of the population have natural immunity & they will not get leprosy even if exposed to infection with M.leprae. Only a few healthy individuals develop signs of leprosy when they come in contact with patients who disseminate bacilli. The immunological status (resistance) varies from person to person and responds as follows when exposed to infection,
i) Natural resistance - No disease will occur.
ii) High resistance - Localized disease (Tuberculoid)
iii) Moderate - Disease fairly localized (Borderline Tuberculoid)
iv) Low resistance - Fairly wide spread (Borderline Lepromatous)
v) No resistance - Wide spread disease (Lepromatous)