The classic sign of early local infection is a circular, outwardly expanding rash called erythema chronicum migrans (also erythema migrans or EM), which occurs at the site of the tick bite 3 to 32 days after being bitten. The rash is red, and may be warm, but is generally painless. Classically, the innermost portion remains dark red and becomes indurated; the outer edge remains red; and the portion in between clears – giving the appearance of a bullseye. However, the partial clearing is uncommon, and thus a true bullseye occurs in as few as 9% of cases.
Erythema migrans is thought to occur in about 80% of infected patients. Patients can also experience flu-like symptoms such as headache, muscle soreness, fever, and malaise.
Lyme disease can progress to later stages even in patients who do not develop a rash.