Leprosy, also known as Hansen's disease (HD), is a long-term infection by the bacterium Mycobacterium leprae or Mycobacterium lepromatosis.[3][4] Initially, infections are without symptoms and typically remain this way for 5 to 20 years.[3] Symptoms that develop include granulomas of the nervesrespiratory tract, skin, and eyes.[3] This may result in a lack of ability to feel pain, thus loss of parts of extremities due to repeated injuries or infection due to unnoticed wounds.[2] Weakness and poor eyesight may also be present.[2]

Leprosy is spread between people.[7] This is thought to occur through a cough or contact with fluid from the nose of an infected person.[7] Leprosy occurs more commonly among those living in poverty.[2] Contrary to popular belief, it is not highly contagious.[2] The two main types of disease are based on the number of bacteria present: paucibacillary and multibacillary.[2] The two types are differentiated by the number of poorly pigmented, numb skin patches present, with paucibacillary having five or fewer and multibacillary having more than five.[2] The diagnosis is confirmed by finding acid-fast bacilli in a biopsy of the skin or by detecting the DNA using polymerase chain reaction.[2]

Leprosy is curable with a treatment known as multidrug therapy.[3] Treatment for paucibacillary leprosy is with the medications dapsone and rifampicin for six months.[2] Treatment for multibacillary leprosy consists of rifampicindapsone, and clofazimine for 12 months.[2] A number of other antibiotics may also be used.[2] These treatments are provided free of charge by the World Health Organization.[3] Globally in 2012, the number of chronic cases of leprosy was 189,000, down from some 5.2 million in the 1980s.[3][8][9] The number of new cases was 230,000.[3] Most new cases occur in 16 countries, with India accounting for more than half.[3][2] In the past 20 years, 16 million people worldwide have been cured of leprosy.[3] About 200 cases are reported per year in the United States.[10]

Leprosy has affected humanity for thousands of years.[2] The disease takes its name from the Latin word lepra, while the term "Hansen's disease" is named after the physician Gerhard Armauer Hansen.[2] Separating people by placing them in leper colonies still occurs in places such as India,[11] China,[12] and Africa.[13] However, most colonies have closed, since leprosy is not very contagious.[13] Social stigma has been associated with leprosy for much of history, which continues to be a barrier to self-reporting and early treatment.[3] Some consider the word "leper" offensive, preferring the phrase "person affected with leprosy".[14] It is classified as a neglected tropical disease.[15] World Leprosy Day was started in 1954 to draw awareness to those affected by leprosy.