The Chicago Department of Public Health confirms an international traveler tested positive for the disease. The person arrived in Chicago on June 17.
Anyone at O'Hare's Terminal Five on that date between 5:50 a.m. and 9:30 a.m. could be at risk.
Measles symptoms, including high fever, cough, runny nose, and a rash, usually appear seven to 21 days after exposure.
The highly contagious disease is preventable through vaccination.
People who believe they may have been exposed should check their vaccination status.
CDPH urged anyone who develops measles symptoms to call a healthcare provider before going to a medical office, urgent care, or emergency department.