Buruli ulcer is an infectious disease caused by bacteria. These bacteria are related to the ones that cause leprosy and those that cause tuberculosis. The disease can be found in tropical regions, but is not limited to the tropics. It is common in Africa, Southeast Asia and Australia. Currently, it is unknown in what way the disease spreads. It often occurs in rural areas close to swamps, rivers, or lakes. For this reason, vector organisms such as mosquitoes appear likely.