Leprosy, also known as Hansen's disease (HD), is a long-term infection by the bacteria Mycobacterium leprae or Mycobacterium lepromatosis. Initially, a person who is infected does not have symptoms and typically remains this way for 5 to 20 years. Symptoms that develop include granulomas of the nerves, respiratory tract, skin, and eyes. This may result in a lack of ability to feel pain, which can lead to the loss of parts of extremities due to repeated injuries or infection due to unnoticed wounds. Weakness and poor eyesight may also be present.
Leprosy is spread between people, although extensive contact is necessary. Spread is thought to occur through a cough or contact with fluid from the nose of a person infected by leprosy. It is not spread during pregnancy to the unborn children or through sexual contact. Leprosy occurs more commonly among those living in poverty. Genetic factors also play a role in susceptibility. The two main types of disease – paucibacillary and multibacillary – 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. The diagnosis is confirmed by finding acid-fast bacilli in a biopsy of the skin or by detecting the bacteria's DNA using polymerase chain reaction.
Leprosy is curable with multidrug therapy. Treatment of paucibacillary leprosy is with the medications dapsone, rifampicin, and clofazimine for six months. Treatment for multibacillary 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. At the end of 2016, there were 173,000 leprosy cases globally, down from some 5.2 million in the 1980s. The number of new cases in 2016 was 216,000. Most new cases occur in 16 countries, with India accounting for more than half. In the past 20 years, 16 million people worldwide have been cured of leprosy. About 200 cases are reported per year 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. Separating people by placing them in leper colonies still occurs in places such as India, China, and Africa. However, most colonies have closed, since leprosy is not very contagious. Social stigma has been associated with leprosy for much of history, which continues to be a barrier to self-reporting and early treatment. Some consider the word "leper" offensive, preferring the phrase "person affected with leprosy". It is classified as a neglected tropical disease. World Leprosy Day was started in 1954 to draw awareness to those affected by leprosy.