Lyme disease was first recognized in the United States in 1975 by Dr. Allen Steere, following a mysterious outbreak of juvenile rheumatoid arthritis near the community of Lyme, Connecticut. The rural location of the Lyme outbreak and the onset of illness during summer and early fall suggested that the transmission of the disease was by an arthropod vector. In 1982, the etiologic agent of Lyme disease was discovered by Willy Burgdorfer, who isolated spirochetes belonging to the genus Borrelia from the mid-guts of Ixodes ticks. He showed that these spirochetes reacted with immune serum from patients that had been diagnosed with Lyme disease. Subsequently, the etiologic agent was given the name Borrelia burgdorferi. Since then, reports of Lyme disease have increased dramatically to the point that the disease has become an important public health problem in some areas of the United States. Today, Lyme disease is the most prevalent tick-borne illness in the United States.