Borrelia burgdorferi is a type of bacteria that causes Lyme disease, a tick-borne illness. It is primarily transmitted to humans through the bite of infected black-legged ticks, also known as deer ticks. The bacteria can lead to various symptoms, including fever, fatigue, and joint pain if not treated promptly. The infection is typically diagnosed through clinical evaluation and laboratory tests. Early treatment with antibiotics is effective in most cases, preventing more severe complications. If left untreated, Borrelia burgdorferi can lead to long-term health issues, affecting the heart, joints, and nervous system.