Buruli ulcer () is an infectious disease characterized by the development of painless open wounds. The disease is limited to certain areas of the world, most cases occurring in Sub-Saharan Africa and Australia. The first sign of infection is a small painless nodule or area of swelling, typically on the arms or legs. The nodule grows larger over days to weeks, eventually forming an open ulcer. Deep ulcers can cause scarring of muscles and tendons, resulting in permanent disability. Buruli ulcer is caused by skin infection with bacteria called Mycobacterium ulcerans. The mechanism by which M. ulcerans is transmitted from the environment to humans is not known, but may involve the bite of an aquatic insect or the infection of open wounds. Once in the skin, M. ulcerans grows and releases the toxin mycolactone, which blocks the normal function of cells, resulting in tissue death and immune suppression at the site of the ulcer. The World Health Organization (WHO) recommends treating Buruli ulcer with a combination of the antibiotics rifampicin and clarithromycin. With antibiotic administration and proper wound care, small ulcers typically heal within six months. Deep ulcers and those on sensitive body sites may require surgery to remove dead tissue or repair scarred muscles or joints. Even with proper treatment, Buruli ulcer can take months to heal. Regular cleaning and dressing of wounds aids healing and prevents secondary infections. In 2018, WHO received 2,713 reports of Buruli ulcer globally. Although rare, it typically occurs in rural areas near slow-moving or stagnant water. The first written description of the disease is credited to Albert Ruskin Cook in 1897 at Mengo Hospital in Uganda. Fifty years later, the causative bacterium was isolated and identified by a group at the Alfred Hospital in Melbourne. In 1998, WHO established the Global Buruli Ulcer Initiative to coordinate global efforts to eliminate Buruli ulcer. WHO considers it a neglected tropical disease. Signs and symptoms The first sign of Buruli ulcer is a painless swollen bump on the arm or leg, often similar in appearance to an insect bite. Sometimes the swollen area instead appears as a patch of firm, raised skin about three centimeters across called a "plaque"; or a more widespread swelling under the skin. Over the course of a few weeks, the original swollen area expands to form an irregularly shaped patch of raised skin. After about four weeks, the affected skin sloughs