CHICAGO — Travelers passing through Chicago Midway International Airport may have been exposed to measles last week, the Illinois Department of Public Health announced.

The department said Thursday an Illinois resident with a now-confirmed diagnosis of measles was on a flight that arrived on Feb. 22 in Concourse B at Midway.

The passenger was not vaccinated and infectious, according to the department.

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Authorities believe people may have been exposed to measles if they were at the airport between 9 p.m. and midnight on Feb. 22.

Most people are vaccinated for the disease in childhood. People who are not vaccinated have a higher risk of catching measles.

The Centers for Disease Control and Prevention said widespread use of measles vaccine resulted in a 99 percent reduction in measles cases compared to the pre-vaccine era.

Note: The Associated Press contributed to this story.

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