Chronic infection caused by bacteria Mycobacteria lepræ and lepromatosis For other uses, see Leprosy (disambiguation) . Leprosy Other names Hansen's disease (HD)  Rash on the chest and abdomen due to leprosy Pronunciation / ˈ l ɛ p r ə s i /  Specialty Infectious disease Symptoms Decreased ability to feel pain  Causes Mycobacterium leprae or Mycobacterium lepromatosis   Risk factors Close contact with a case of leprosy, living in poverty   Treatment Multidrug therapy  Medication Rifampicin , dapsone , clofazimine  Frequency 209,000 (2018)  Leprosy , also known as Hansen's disease ( HD ), is a long-term infection by the bacteria Mycobacterium leprae or Mycobacterium lepromatosis .   Infection can lead to damage of the nerves , respiratory tract , skin, and eyes.  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.  An infected person may also experience muscle weakness and poor eyesight.  Leprosy symptoms may begin within one year, but for some people symptoms may take 20 years or more to occur.  Leprosy is spread between people, although extensive contact is necessary.   About 95% of people who contract M. leprae do not develop the disease.  Spread is thought to occur through a cough or contact with fluid from the nose of a person infected by leprosy.   Genetic factors and immune function play a role in how easily a person catches the disease.   Leprosy does not spread during pregnancy to the unborn child, or through sexual contact.  Leprosy occurs more commonly among people living in poverty.  There are two main types of the disease – paucibacillary and multibacillary, which differ in the number of bacteria present.  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.  The diagnosis is confirmed by finding acid-fast bacilli in a biopsy of the skin.  Leprosy is curable with multidrug therapy.  Treatment of paucibacillary leprosy is with the medications dapsone , rifampicin , and clofazimine for six months.  Treatment for multibacillary leprosy uses the same medications for 12 months.  A number of other antibiotics may also be used.  These treatments are provided free of charge by the World Health Organization .  People with leprosy can live with their families and go to school and work.  In 2018, there were 209,000 leprosy cases globally, down from 5.2 million in the 1980s.    The number of new cases in 2016 was 216,000.  Most new cases occur in 14 countries, with India accounting for more than half.   In the 20 years from 1994 to 2014, 16 million people worldwide were cured of leprosy.  About 200 cases per year are reported in the United States.  Leprosy has affected humanity for thousands of years.  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 .  Leprosy has historically been associated with social stigma , which continues to be a barrier to self-reporting and early treatment.  Separating people affected by leprosy by placing them in leper colonies still occurs in some areas of India,  China,  Africa,  and Thailand.  Most colonies have closed, as leprosy is not very contagious.  Some consider the word "leper" offensive, preferring the phrase "person affected with leprosy".  Leprosy is classified as a neglected tropical disease .  World Leprosy Day was started in 1954 to draw awareness to those affected by leprosy.  Contents 1 Signs and symptoms 2 Cause 2.1 M. leprae and M. lepromatosis 2.2 Risk factors 2.3 Transmission 2.4 Genetics 3 Mechanism 4 Diagnosis 4.1 Classification 5 Prevention 6 Treatment 6.1 Anti-leprosy medication 6.2 Skin changes 7 Epidemiology 7.1 Disease burden 8 History 9 Society and culture 9.1 India 9.2 Treatment cost 9.3 Historical texts 9.4 Middle Ages 9.5 19th century 9.5.1 Norway 9.5.2 Colonialism and imperialism 9.6 Stigma 9.7 Programs and treatment 10 Notable cases 11 Coverage in the media 12 Other animals 13 See also 14 References 15 Further reading 16 External links Signs and symptoms [ edit ] Common symptoms present in the different types of leprosy include a runny nose; dry scalp; eye problems; skin lesions; muscle weakness; reddish skin; smooth, shiny, diffuse thickening of facial skin, ear, and hand; loss of sensation in fingers and toes; thickening of peripheral nerves; a flat nose due to destruction of nasal cartilage; and changes in phonation and other aspects of speech production.   In addition, atrophy of the testes and impotence may occur.  Leprosy can affect people in different ways.  The average incubation period is 5 years.  People may begin to notice symptoms within the first year or up to 20 years after infection.  The first noticeable sign of leprosy is often the development of pale or pink coloured patches of skin that may be insensitive to temperature or pain.  Patches of discolored skin are sometimes accompanied or preceded by nerve problems including numbness or tenderness in the hands or feet.   Secondary infections (additional bacterial or viral infections) can result in tissue loss, causing fingers and toes to become shortened and deformed, as cartilage is absorbed into the body.   A person's immune response differs depending on the form of leprosy.  Approximately 30% of people affected with leprosy experience nerve damage.  The nerve damage sustained is reversible when treated early, but becomes permanent when appropriate treatment is delayed by several months. Damage to nerves may cause loss of muscle function, leading to paralysis. It may also lead to sensation abnormalities or numbness , which may lead to additional infections, ulcerations, and joint deformities.  Paucibacillary leprosy (PB): Pale skin patch with loss of sensation Skin lesions on the thigh of a person with leprosy Hands deformed by leprosy Cause [ edit ] M. leprae and M. lepromatosis [ edit ] Main articles: Mycobacterium leprae and Mycobacterium lepromatosis M. leprae , one of the causative agents of leprosy: As an acid-fast bacterium, M. leprae appears red when a Ziehl-Neelsen stain is used. M. leprae and M. lepromatosis are the mycobacteria that cause leprosy.  M. lepromatosis is a relatively newly identified mycobacterium isolated from a fatal case of diffuse lepromatous leprosy in 2008.   M. lepromatosis is indistinguishable clinically from M. leprae .  M. leprae is an intracellular, acid-fast bacterium that is aerobic and rod-shaped.  M. leprae is surrounded by the waxy cell envelope coating characteristic of the genus Mycobacterium .  Genetically, M. leprae and M. lepromatosis lack the genes that are necessary for independent growth.  M. leprae and M. lepromatosis are obligate intracellular pathogens , and can not be grown ( cultured ) in the laboratory.  The inability to culture M. leprae and M. lepromatosis has resulted in a difficulty definitively identifying the bacterial organism under a strict interpretation of Koch's postulates .   While the causative organisms have to date been impossible to culture in vitro , it has been possible to grow them in animals such as mice and armadillos .   Naturally occurring infection has been reported in nonhuman primates (including the African chimpanzee , the sooty mangabey , and the cynomolgus macaque), armadillos,  and red squirrels .  Multilocus sequence typing of the armadillo M. leprae strains suggests that they were of human origin for at most a few hundred years.  Thus, it is suspected that armadillos first acquired the organism incidentally from early American explorers.  This incidental transmission was sustained in the armadillo population, and it may be transmitted back to humans, making leprosy a zoonotic disease (spread between humans and animals).  Red squirrels ( Sciurus vulgaris ) , a threatened species in Great Britain , were found to carry leprosy in November 2016.  It has been suggested that the trade in red squirrel fur, highly prized in the medieval period and intensively traded, may have been responsible for the leprosy epidemic in medieval Europe.  A pre-Norman-era skull excavated in Hoxne, Suffolk , in 2017 was found to carry DNA from a strain of Mycobacterium leprae, which closely matched the strain carried by modern red squirrels on Brownsea Island , UK.   Risk factors [ edit ] The greatest risk factor for developing leprosy is contact with another person infected by leprosy.  People who are exposed to a person who has leprosy are 5–8 times more likely to develop leprosy than members of the general population.  Leprosy also occurs more commonly among those living in poverty.  Not all people who are infected with M. leprae develop symptoms.   Conditions that reduce immune function, such as malnutrition, other illnesses, or genetic mutations, may increase the risk of developing leprosy.  Infection with HIV does not appear to increase the risk of developing leprosy.  Certain genetic factors in the person exposed have been associated with developing lepromatous or tuberculoid leprosy.  Transmission [ edit ] Transmission of leprosy occurs during close contact with those who are infected.  Transmission of leprosy is not well understood, but the upper respiratory tract is thought to be the most likely entry route.   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.