Health officials have issued a measles exposure warning for Chicago’s O’Hare International Airport, after an infected individual spent several hours in Terminal 1 on April 22 and 23 between 10 a.m. and 8 p.m. Hundreds of travelers may have been exposed. The patient had received one dose of the MMR vaccine but still developed symptoms and tested positive for measles.

A second measles case was reported in the same Illinois county shortly after, though any connection between the two cases remains unclear. Measles spreads through coughing and sneezing and can linger in the air for up to two hours, making confined spaces like airports high-risk.

Health experts emphasize vaccination as the best protection, noting that two doses of the MMR vaccine provide about 97% effectiveness. People unsure of their immunization status are advised to review their records and get vaccinated if needed.

Anyone present in Terminal 1 during the exposure window should monitor for symptoms such as fever, cough, runny nose, red eyes, and rash. Those exhibiting symptoms are urged to contact a healthcare provider before visiting clinics to avoid spreading the virus further.