CHICAGO — Health officials on Thursday said an Illinois resident has been diagnosed with measles. That that person recently took a flight to Chicago Midway International Airport.

In a statement, Illinois Department of Public Health officials said the passenger arrived in Concourse B on Feb. 22 and was unvaccinated and infectious on that day.

Local and state health departments said they are “investigating this isolated case.”

According to the statement, people may have been exposed to measles if they were at Midway between 9 p.m. and midnight Feb. 22.

The passenger sought treatment at the emergency room at Northwestern Medicine Delnor Hospital in suburban Geneva on Feb. 24. People who were in the emergency room between 11:45 a.m. and 2:15 p.m. that day also may have been exposed.

Additionally, anyone who was anywhere in the hospital from 4 to 6:15 p.m. Feb. 24 or 10 a.m. to 1 p.m. Feb. 25 could have been exposed.

“These are the only known public locations in Illinois where exposures occurred,” officials said in a statement.

People who are infected could develop symptoms as late as March 20. These include a rash, high fever, a cough, a runny nose and red, watery eyes.

Measles can cause serious complications, such as pneumonia and encephalitis. Measles is easily spread through the air when someone coughs or sneezes. People can also get sick when they come into contact with mucus or saliva from an infected person.

If you develop symptoms, health officials recommend you call or email a health care provider before going to a medical office or emergency room.

For more information about measles, visit the Illinois Department of Public Health website.