Leprosy, also known as Hansen's disease (HD), is a chronic infection caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis. Initially, infections are without symptoms and typically remain this way for 5 to as long as 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 and thus loss of parts of extremities due to repeated injuries. Weakness and poor eyesight may also be present.The two main types of disease are based on the number of bacteria present: paucibacillary and multibacillary. 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. The diagnosis is confirmed by finding acid-fast bacilli in a biopsy of the skin or via detecting the DNA by polymerase chain reaction. It occurs more commonly among those living in poverty and is believed to be transmitted by respiratory droplets. It is not very contagious.Leprosy is curable with treatment. Treatment for paucibacillary leprosy is with the medications dapsone and rifampicin for 6 months. Treatment for multibacillary leprosy consists of rifampicin, dapsone, and clofazimine for 12 months. These treatments are provided for free by the World Health Organization. A number of other antibiotics may also be used. Globally in 2012, the number of chronic cases of leprosy was 189,000 and the number of new cases was 230,000. The number of chronic cases has decreased from some 5.2 million in the 1980s. 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 Latin word lepra, which means "scaly", while the term "Hansen's disease" is named after the physician Gerhard Armauer Hansen. Separating people in leper colonies still occurs in countries like India, with more than a thousand; China, with around hundreds; and in Africa. However, most colonies have closed. Leprosy has been associated with social stigma for much of history, which remains a barrier to self-reporting and early treatment. World Leprosy Day was started in 1954 to draw awareness to those affected by leprosy.