A multisystem illness caused by the tick-borne spirochete Borrelia burgdorferi. The disease, also known as Lyme borreliosis, generally begins with a unique expanding skin lesion, erythema migrans, which is often accompanied by symptoms resembling those of influenza or meningitis. During the weeks or months following the tick bite, some individuals may develop cardiac and neurological abnormalities, particularly meningitis or inflammation of the cranial or peripheral nerves. If the disease is untreated, intermittent or chronic arthritis and progressive encephalomyelitis may develop months or years after primary infection.