The erythema migrans is an indication of previous recent infection. It is not due to the current bite as the incubation is generally 7 to 10 days. Erythema migrans occurs in 60 to 80 percent of cases and is generally accompanied by mild constitutional symptoms which should be sought in the history and review of symptoms.

{Ref: Spach DH, Liles WC, Campbell GL, et al. Tick-Borne Diseases in the United States. New Engl J Med 1993; 329:936-47.}