Color enhanced scanning electron micrograph (SEM) of the bacterium, Borrelia burgdorferi, the cause of Lyme disease. These bacterial spirochetes are transmitted by the bite of infected deer ticks and cause more than 16,000 infections in the U.S. each year. Early symptoms of Lyme disease include a characteristic "bull's-eye" rash and erythema migraines, accompanied by nonspecific symptoms such as fever, malaise, fatigue, headache, muscle, and joint aches. If left untreated, infection may cause swelling and pain in large joints like the knee. Cognitive disorders such as sleep disturbance, fatigue and personality changes have also been known to develop in advanced cases. SEM at 1,700x.