An infection, also called Hansen's disease, caused by bacteria that leads to skin lesions and nerve damage.

Leprosy is caused by bacteria called Mycobacterium leprae, spread mostly by droplets from a cough or sneeze. But it takes close contact over a long time to spread the bacteria. After exposure, most people clear the bacteria without developing leprosy. Some develop leprosy, which if untreated can lead to serious disability.

The bacteria that cause leprosy can take years to show symptoms. An early symptom is a small bump where the skin is lighter than typical. Other symptoms may be more bumps, weakness, or pain from nerve damage or numbness.

Medicines that target bacteria, called antibiotics, are used together to treat leprosy.