Lyme is a tick-borne disease caused by the bacterium Borrelia burgdorferi. It is transmitted to humans through the bite of an infected blacklegged tick, commonly known as a deer tick. Symptoms of Lyme disease can include fever, headache, fatigue, and a characteristic skin rash called erythema migrans. If left untreated, infection can spread to joints, the heart, and the nervous system. Treatment for Lyme disease is typically antibiotics.