In former times, leprosy was present worldwide, whereas nowadays, it is exterminated in developped countries. In the third world and in emergent nations, the disease is still present, mainly in South-East Asia, in India, and in Africa and Brazil. The prevalence has decreased in the last years , which can be traced back to the success of the triple combination therapy at the beginning of the 80s. 1991 the WHO declared it a goal to eliminate leprosy as a world healh problem till 2000, meaning to lower the prevalence below 1:10,000. Regarding the world's population, this has succeeded with the therapeutical possibilities and the support of a wide-spread application, whereat further efforts in some singular countries are still necessary.
The number of new cases (incidents) stagnates in the last years. People living in severe poverty are mainly affected.
Mycobacterium leprae is, like the tuberculosis pathogen, an intracellularly living acid-resistant rod bacterium.
In contrast to belief spread worldwide, the pathogen is little virulent. Source of infection is the sick person and a transmission is only possible via an intensive, direct, longer contact with lesioned skin, mucosa, or bloody sniffles (highest danger of transmission). The lepromatous form of leprosy is way more contagious than the tuberculoid form, because the level of mycobacteria in skin and mucosa is much higher there.