Borrelia is a genus of bacteria known for causing Lyme disease and other tick-borne illnesses. These spiral-shaped bacteria are primarily transmitted to humans through the bite of infected ticks, particularly the black-legged tick and the western black-legged tick. There are several species of Borrelia, with Borrelia burgdorferi being the most common in North America. Symptoms of infections can include fever, fatigue, and a characteristic skin rash called erythema migrans. Early diagnosis and treatment with antibiotics are crucial to prevent more severe complications.