Borrelia , which can be transmitted from infected animals to humans by ticks. The ticks are commonly found in the western United States, West Africa, and various tropical and subtropical regions of the world. Delirium may occur. The fever rises to a peak during the following 5 to 10 days and then suddenly falls. After a short period of a day or two, a relapse occurs, often accompanied by jaundice, and the pattern of symptoms is repeated, but without the rash.
Most cases respond to treatment with antibiotic drugs.