Society and culture
India
British India enacted the Leprosy Act of 1898 which institutionalized those affected and segregated them by sex to prevent reproduction. The act was difficult to enforce but was repealed in 1983 only after multidrug therapy had become widely available. In 1983, the National Leprosy Elimination Programme, previously the National Leprosy Control Programme, changed its methods from surveillance to the treatment of people with leprosy. India still accounts for over half of the global disease burden. According to WHO, new cases in India during 2019 diminished to 114,451 patients (57% of the worlds total new cases). Until 2019, one could justify a petition for divorce with the spouses diagnosis of leprosy. Treatment cost
Between 1995 and 1999, the WHO, with the aid of the Nippon Foundation, supplied all endemic countries with free multidrug therapy in blister packs, channeled through ministries of health. This free provision was extended in 2000 and again in 2005, 2010 and 2015 with donations by the multidrug therapy manufacturer Novartis through the WHO. In the latest agreement signed between the company and the WHO in October 2015, the provision of free multidrug therapy by the WHO to all endemic countries will run until the end of 2025. At the national level, nongovernment organizations affiliated with the national program will continue to be provided with an appropriate free supply of multidrug therapy by the WHO. Historical texts
Written accounts of leprosy date back thousands of years. Various skin diseases translated as leprosy appear in the ancient Indian text, the Atharava Veda, by 600 BC.
Older research suggested the skin as the main route of transmission, but recent research has increasingly favored the respiratory route.Leprosy is not sexually transmitted and is not spread through pregnancy to the unborn child. The majority (95%) of people who are exposed to M. leprae do not develop leprosy; casual contact such as shaking hands and sitting next to someone with leprosy does not lead to transmission. People are considered non-infectious 72 hours after starting appropriate multi-drug therapy.Two exit routes of M. leprae from the human body often described are the skin and the nasal mucosa, although their relative importance is not clear. Lepromatous cases show large numbers of organisms deep in the dermis, but whether they reach the skin surface in sufficient numbers is doubtful.Leprosy may also be transmitted to humans by armadillos, although the mechanism is not fully understood. Genetics
Not all people who are infected or exposed to M. leprae develop leprosy, and genetic factors are suspected to play a role in susceptibility to an infection. Cases of leprosy often cluster in families and several genetic variants have been identified. In many people who are exposed, the immune system is able to eliminate the leprosy bacteria during the early infection stage before severe symptoms develop. A genetic defect in cell-mediated immunity may cause a person to be susceptible to develop leprosy symptoms after exposure to the bacteria.