Leprosy is a chronic disease caused by a bacillus, Mycobacterium leprae, an acid-fast, rod-shaped bacillus. Leprosy mainly affects the skin, the peripheral nerves, mucosa of the upper respiratory tract and the eyes, apart from some other structures. Depending on the bacillary load, the disease can be classified as either paucibacillary or multibacillary. M. leprae multiplies very slowly and the incubation period of the disease is about five years. Symptoms can take as long as 20 years to appear.

    Leprosy is not highly infectious. It is transmitted via droplets, from the nose and mouth, during close and frequent contacts with untreated cases. Leprosy is curable and treatment provided in the early stages averts disability. The diagnosis and treatment of leprosy today is easy and most endemic countries are striving to fully integrate leprosy services into existing general health services. This is especially important for those under-served and marginalized communities most at risk from leprosy, often the poorest of the poor.