Officials in Montgomery County say the unidentified resident had traveled to Malawi in southern Africa. An outbreak there killed dozens of people and sickened thousands more this year.
Montgomery County officials say the affected resident had visited several area grocery stores and health facilities between July 27 and Aug. 3, as well as Philadelphia International Airport and Longport, N.J.
Measles can be spread through sneezing, coughing and other close contact.
Pennsylvania law requires all children attending school or licensed day car facilities to be immunized against measles.