CHICAGO (WLS) — The Chicago Department of Public Health and Cook County Department of Public Health have identified the first two cases of measles in Cook County this year, the agencies said Wednesday evening.

The possible measles exposure included Chicago’s O’Hare International Airport, one of the world’s busiest airports. There were two days last week in Terminal 1 when passengers may have been exposed, and now officials are asking anyone who isn’t vaccinated who was there on those days to call their doctor.

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One case is an adult, who is a suburban Cook County resident, and whose vaccination status is unknown, health officials said. They went to a local hospital on Monday, officials said.

The other case is an adult Chicago resident, who traveled internationally through O’Hare Airport in early April, officials said. That person had one prior dose of MMR vaccine. The person had a rash onset on Friday, and has been isolated at home since being diagnosed.

“It’s really important that they confirm that they’re vaccinated, and if they have any questions or concerns about their vaccination status, they should talk to their primary care provider,” said Dr. Kiran Joshi with the Cook County Department of Public Health.

The health department shared the following locations and times for points of potential public exposure:

– April 21: Chicago Public Library – Independence Branch, 4024 N. Elston Ave.
– April 21: Fittingly Delicious, 3939 W. Irving Park Road
-April 22: O’Hare airport, between 10 a.m. and 8 p.m., especially Terminal 1
– April 23: O’Hare airport, between 10 a.m. and 8 p.m., especially Terminal 1
– Friday: Aldi. 7235 39th St., Lyons, between 10 a.m.-12:30 p.m.
– Sunday: Shell. 3901 S. Harlem Ave., Stickney, between 10 a.m.-12:30 p.m.
– Monday: Mobil, 2945 S. Harlem Ave, Berwyn, between 10:20 a.m.-1 p.m.

The two cases are the first Cook County cases this year, but they are likely not the last.

“I would not be surprised if cases rise, either associated with these two individuals or unassociated with them,” said Dr. Nicholas Cozzi with RUSH University Medical Center.

Those who may have been exposed should tell healthcare providers, if they are unsure about their vaccination status. The healthcare provider will determine the need for testing if symptoms develop.

“About 95%t of cases are unvaccinated individuals,” Dr. Cozzi said.

If an exposed person develops symptoms, her or she should notify his or her healthcare provider or a healthcare facility before going to a medical office or emergency department for evaluation to ensure that special arrangements can be made to prevent other patients and medical staff from possible exposure.

“Most individuals are vaccinated against measles routinely in childhood and are not at high risk. The best defense against measles is vaccination. Two doses of MMR vaccine are 97% effective against measles and generally provide lifelong immunity,” health officials said.

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The Illinois Department of Public Health reported the first case of measles in the state in 2025 last week.

That patient is an adult in far southern Illinois.

An outbreak in Chicago early last year led to 67 cases.

Earlier this month, Indiana health officials announced at least six cases in Allen County, which is in the area around Fort Wayne.

Measles is highly contagious, and is spread when an infected person sneezes or coughs.

Illinois officials said the risk of measles transmission for the general public in Illinois remains low.

Those who plan to travel internationally should ensure they have received two doses of MMR at least two weeks prior to travel, or have other evidence of immunity.

Local health departments are working together to identify and notify people who may have been exposed.

“We are experiencing a resurgence of measles in the United States, despite the fact that two doses of the MMR vaccine can prevent it. Misinformation has contributed to declining vaccination rates and fueled recent outbreaks. The MMR vaccine has been in use for over 50 years, is highly effective, and has protected millions of lives,” interim CCDPH Chief Operating Officer Dr. Kiran Joshi said.

Where to get vaccinated

To make an appointment for measles vaccination at a Cook County Healthcommunity health center in Chicago or suburban Cook County call 833-308-1988.

Unvaccinated individuals who do not have a healthcare provider are encouraged to contact Cook County Health at 833-308-1988 to schedule a vaccination appointment.

Chicago Department of Public Health (CDPH) offersfreeMMR vaccinations for anyone who needs them, regardless of insurance status, atCDPH Immunization Clinicsthroughout the city. Walk-ins are welcome, but registration is highly encouraged. Create an account and register for an appointment atgetvaxchi.chicago.govor by calling the clinic.

Visit cookcountypublichealth.org/communicable-diseases/measles for more information.