Leprosy or Hansen's disease is a chronic infectious disease caused by the bacterium Mycobacterium leprae. Leprosy is primarily a granulomatous disease of the peripheral nerves, mucosa of the upper respiratory tract, and produces skin lesions. If left untreated, there can be progressive and permanent damage to the skin, nerves, limbs and eyes. Contrary to the common popular conception of the illness, it does not cause body parts to simply fall off, and it differs from tzaraath, the malady described in the Hebrew scriptures and previously translated into English as leprosy.
Leprosy has affected humanity since at least 600 BC, and was well-recognized in the civilizations of ancient China, Egypt and India. In 1995, the World Health Organization (WHO) estimated that between two and three million individuals were permanently disabled because of leprosy. Although the forced quarantine or segregation of patients is unnecessary, and can be considered unethical, a few leper colonies still remain around the world, in countries such as India, Vietnam, and the Philippines.
The age-old stigma associated with the advanced form of the disease still lingers in many areas, and remains a major obstacle to self-reporting and early treatment. Effective treatment for leprosy appeared in the late 1940s with the introduction of dapsone and its derivatives. However, leprosy bacilli resistant to dapsone gradually appeared and became widespread, and it was not until the introduction of multidrug therapy (MDT) in the early 1980s that the disease could be diagnosed and treated successfully within the community.