Bartonella bacilliformis is a type of bacteria that causes the disease known as Carrion's disease. It is primarily transmitted to humans through the bite of infected sandflies, particularly in regions of South America, such as Peru and Ecuador. The infection can lead to two distinct phases: an acute phase characterized by fever and skin lesions, and a chronic phase that can result in severe anemia. This bacterium is a gram-negative rod and is part of the Bartonella genus. Diagnosis typically involves blood tests, and treatment usually includes antibiotics. Preventive measures focus on avoiding sandfly bites, especially in endemic areas.