Illinois health officials issued an advisory after a confirmed measles case was linked to Chicago O’Hare International Airport. The infected individual spent significant time in Terminal 1 on April 22 and 23, potentially exposing travelers, visitors, and airport staff. Officials said the person had received one dose of the MMR vaccine, which provides partial protection. Symptoms began with fever and respiratory illness before a measles rash developed. The patient is now isolating at home. Health authorities are conducting contact tracing and advising those potentially exposed to monitor for symptoms for 21 days. Vaccination remains the best protection against measles.