Travelers at Chicago Midway Airport late last week may have been exposed to measles, the Illinois Department of Public Health (IDPH) said in a warning Thursday.

An Illinois resident, who the health department did not identify, arrived last Friday at Concourse B at the Chicago Midway Airport. At the time, he or she was unvaccinated and infectious for measles.

The IDPH did not disclose the infected person’s flight number or what airline they were using.

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“People may have been exposed to measles if they were at Midway Airport on February 22, 2019, between 9 p.m. and midnight,” the health department said, adding two days later, on Feb. 24, he or she went to the Northwestern Medicine Delnor Hospital’s emergency department for treatment. This means those who were at the emergency department between 11:45 a.m. and 2:15 p.m. may have also been exposed to measles, as well as those who at the hospital from 4:00 p.m. to 6:15 p.m. the same day. Additionally, those who were at the hospital from 10:00 a.m. - 1:00 p.m. on Feb. 25 may have also been exposed.

“These are the only known public locations in Illinois where exposures occurred,” the health department said.

Measles is a highly contagious viral infection that is spread in the air when an infected person coughs or sneezes. However, people can also contract measles when they “come in contact with mucus or saliva from an infected person,” the IDPH says.

"Getting vaccinated not only protects you, it protects others around you who are too young to get the vaccine or cannot receive it for medical reasons." — Ngozi Ezike

Though symptoms sometimes do not appear for weeks, typical signs of measles include a high fever, rash, cough, and red, watery eyes.

Common complications include ear infections and diarrhea, but more severe complications — such as pneumonia, encephalitis (swelling of the brain) — can also occur, according to the Centers for Disease Control and Prevention (CDC).

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“Measles is highly contagious. However, two doses of measles vaccine are about 97 percent effective in preventing measles,” IDPH Director Ngozi Ezike said in the statement. “We urge everyone to make sure they and their family members are up-to-date on measles/mumps/rubella (MMR) vaccine and all other age-appropriate immunizations, especially if you are traveling to other countries where measles is regularly found.

“Getting vaccinated not only protects you, it protects others around you who are too young to get the vaccine or cannot receive it for medical reasons,” Ezike added.

However, those who were vaccinated “routinely” in childhood are not at high risk for contracting measles, according to the IDPH.