Leprosy, also known as Hansen's disease (HD), is a long-term infection by the bacteria Mycobacterium leprae or Mycobacterium lepromatosis.[4][8] Infection can lead to damage of the nerves, respiratory tract, skin, and eyes.[4] This nerve damage may result in a lack of ability to feel pain, which can lead to the loss of parts of a person's extremities from repeated injuries or infection due to unnoticed wounds.[3] An infected person may also experience muscle weakness and poor eyesight.[3] Leprosy symptoms may begin within one year, but, for some people, symptoms may take 20 years or more to occur.[4]

Other namesHansen's disease (HD)[1]
Rash on the chest and abdomen due to leprosy
SpecialtyInfectious disease
SymptomsDecreased ability to feel pain[3]
CausesMycobacterium leprae or Mycobacterium lepromatosis[4][5]
Risk factorsClose contact with a case of leprosy, living in poverty[3][6]
TreatmentMultidrug therapy[4]
MedicationRifampicin, dapsone, clofazimine[3]
Frequency209,000 (2018)[7]

Leprosy is spread between people, although extensive contact is necessary.[3][9] Leprosy has a low pathogenicity, and 95% of people who contract M. leprae do not develop the disease.[10] Spread is thought to occur through a cough or contact with fluid from the nose of a person infected by leprosy.[9][10] Genetic factors and immune function play a role in how easily a person catches the disease.[10][11] Leprosy does not spread during pregnancy to the unborn child or through sexual contact.[9] Leprosy occurs more commonly among people living in poverty.[3] There are two main types of the disease – paucibacillary and multibacillary, which differ in the number of bacteria present.[3] A person with paucibacillary disease has five or fewer poorly-pigmented, numb skin patches, while a person with multibacillary disease has more than five skin patches.[3] The diagnosis is confirmed by finding acid-fast bacilli in a biopsy of the skin.[3]

Leprosy is curable with multidrug therapy.[4] Treatment of paucibacillary leprosy is with the medications dapsone, rifampicin, and clofazimine for six months.[10] Treatment for multibacillary leprosy uses the same medications for 12 months.[10] A number of other antibiotics may also be used.[3] These treatments are provided free of charge by the World Health Organization.[4] People with leprosy can live with their families and go to school and work.[12] In 2018, there were 209,000 leprosy cases globally, down from 5.2 million in the 1980s.[7][13][14] The number of new cases in 2016 was 216,000.[4] Most new cases occur in 14 countries, with India accounting for more than half.[3][4] In the 20 years from 1994 to 2014, 16 million people worldwide were cured of leprosy.[4] About 200 cases per year are reported in the United States.[15]

Leprosy has affected humanity for thousands of years.[3] The disease takes its name from the Greek word λέπρᾱ (léprā), from λεπῐ́ς (lepís; "scale"), while the term "Hansen's disease" is named after the Norwegian physician Gerhard Armauer Hansen.[3] Leprosy has historically been associated with social stigma, which continues to be a barrier to self-reporting and early treatment.[4] Separating people affected by leprosy by placing them in leper colonies still occurs in some areas of India,[16] China,[17] areas in the African continent,[18] and Thailand.[19] Most colonies have closed, as leprosy is not very contagious.[18] Some consider the word leper offensive, preferring the phrase "person affected with leprosy".[20] Leprosy is classified as a neglected tropical disease.[21] World Leprosy Day was started in 1954 to draw awareness to those affected by leprosy.[22]