Chicago O’Hare International Airport was put on high alert after health officials confirmed a measles exposure involving an adult traveler who spent hours in Terminal 1 on April 22–23. The traveler, who had received only one MMR dose, moved through crowded areas during peak travel times, potentially exposing thousands of people.

Measles is one of the most contagious viruses known and can linger in the air for up to two hours, making airports especially risky. Officials quickly launched emergency protocols, warning travelers and staff as they tracked possible contacts. The infected individual developed symptoms after leaving the airport and was isolated, limiting further spread, but a second case soon appeared in the same county, raising concerns about community transmission.

Health authorities urged anyone who passed through Terminal 1 during that window to watch for symptoms and seek medical advice if needed, while stressing a familiar message: completing the two-dose MMR vaccine remains essential to preventing outbreaks in highly connected places like major airports.