Mycobacterium leprae is the major cause of Hansen's disease, often known as leprosy. Natural infection has been reported in species other than humans, including mangabey monkeys and armadillos. Infection has also been reported after contact with infected tissues or fluids from dogs, pigs, cows, and wild mammals. No evidence supports transmission from animal to animal. Leprosy is a chronic bacterial disease that usually affects the skin and peripheral nerves. It is caused by Mycobacterium leprae, which mainly infects macrophages. The bacteria spread when an infected person scratches himself or herself, coughs, or bites his or her nose, mouth, or fingers. Leprosy can also be passed from mother to child during pregnancy or through breast milk. People are most likely to get leprosy if they live in remote areas of Nepal, India, Brazil, Indonesia, and Madagascar. Otherwise healthy people sometimes develop symptoms after being exposed to M. leprae. Symptoms include loss of feeling in your feet and hands, muscle weakness, blindness, and nerve damage that leads to numbness or paralysis. If left untreated, leprosy can result in permanent disability or death. The only way to prevent leprosy is by avoiding exposure to the bacteria that cause it.