This is a case report of an american woman who consulted in our country for multiple erythema migrans, from which a Lyme disease was diagnosed. This infectious disease is caused by spirochetes from the Borrelia burgdorferi sensu lato complex (Bbsl) and is transmitted by the bite of ticks. Traditionally Bbsl had been detected in ticks only in the Northern Hemisphere. However, since 2013 there have been reports in South America. In Chile, Borrelia chilensis was recently described, which does not have an associated disease in humans. Aspects of the infectious agent, its epidemiology, its vectors and new findings in South America are discussed. Likewise, the clinical diagnostic criteria, laboratory and appropriate treatment are proposed, according to the stage in their natural history.