It is a chronic infection caused by a bacteria called Mycobacterium leprae. Leprosy causes changes in the body which are often evident in a person's appearance. Skin lesions appear on the body, arms, legs, and face. Many of these lesions produce damage to the sensory nerves, which makes the skin numb in these areas. As the disease progresses, tissues are destroyed, and the lack of pain sensation leads to traumatic injuries to the hands and feet.
Open sores are a pathway to infections, which are the cause of death in many cases.
Persons with leprosy cannot hide their disease. It is visible on their faces and bodies. I try to imagine the fear they experienced in those years before modern medical treatment could arrest and cure the disease. But the physical distress, and the emotional response to a future of disease and death, were only part of the burden of the leper. It's likely that the designation was at first a hygenic one, meant to prevent the spread of the disease from one person to another.