Cases of the highly infectious disease measles are popping up in cities and states across the country, including in Illinois, where at least two new cases were reported in the Chicago area, one involving a person who recently passed through O'Hare, one of the world's busiest airports.
One of the cases was detected in a suburban Cook County adult, health officials said. The person received care at a local hospital on April 28 and has since been quickly isolated.
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WATCH HEREThe second case was identified in an adult Chicago resident who had recently traveled internationally through O'Hare International Airport in early April and had received one prior dose of the MMR vaccine, according to officials.
That patient had a rash onset on April 25 and has since been isolated at home, officials said.
Earlier this month, health officials confirmed a measles case in southern Illinois, marking the first measles case in the state in 2025.
But what exactly is measles, what are the symptoms, and how can you tell if you have been vaccinated? Here's what to know.
What is measles?
Measles is a respiratory virus that can survive in the air for up to two hours. Up to nine out of 10 people who are susceptible will get the virus if exposed, according to the U.S. Centers for Disease Control and Prevention. Most kids will recover from the measles if they get it, but infection can lead to dangerous complications like pneumonia, blindness, brain swelling and death.
"Some people think of measles as just a little rash and fever that clear up in a few days. But measles can cause serious health complications, especially in children younger than 5 years old," the CDC's website states.
Measles symptoms
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SIGN UP Measles typically starts with cough, runny nose, red eyes, and a fever that can get very high, CDPH reported.
A rash commonly develops within three to five days of those early symptoms appearing.
"The rash looks like tiny, red spots that start at the head and spread down to the rest of the body," the department stated.
According to the CDC, symptoms typically appear within seven to 14 days of exposure to the virus.
Complications are possible, particularly for children under the age of 5. The complications range from ear infections and diarrhea to more serious issues like pneumonia and encephalitis.
Where has measles been reported in Illinois and Chicago?
According to the Illinois Department of Public Health, the state's first case of measles for 2025 was detected in April 23 in far southern Illinois. The case marks the first in Illinois since an outbreak in Chicago in early 2024 that resulted in a total of 67 cases. Most of those cases were in migrants, officials said at the time.
According to the IDPH, seven locations related to the southern Illinois case were identified as "sites of potential exposures" between April 7 and April 15. They can be found below:
- Don Sol Restaurant, Marion IL
- Legacy Fitness, Marion IL
- Walmart, Marion IL
- Kroger Grocery, Marion IL
- Wonder Wash Laundry, Marion IL
- Easy Coin Laundry, Marion IL
- Small Star Laundry, Marion IL
Wednesday, officials with Cook County and the Chicago Department of Public Health said two cases were reported in the Chicago area.
According to the Illinois Department of Public Health, seven locations have been identified as "sites of potential exposures" between April 7 and April 15.1
According to public health officials, the following locations are possible points of public exposure:
- Monday 4/21/2025: Fittingly Delicious, 3939 W. Irving Park Rd.
- Tuesday 04/22/2025: O’Hare Airport, 10 a.m. –8 p.m., especially Terminal 1
- Wednesday 04/23/2025: O’Hare Airport, 10 a.m.–8 p.m., especially Terminal 1
- Friday 04/25/2025: Aldi: 7235 39th St, Lyons, IL 6053, 10 a.m.-12:30 p.m.
- Sunday 04/27/2025 Shell: 3901 S. Harlem Ave., Stickney, IL 60402, 10 a.m.-12:30 p.m.
- Monday 04/28/2025 Mobil: 2945 S. Harlem Ave, Berwyn, IL 60402, 10:20 a.m-1 p.m.
How to know if you've gotten the measles vaccines
The measles, mumps and rubella vaccine — which is considered safe and highly effective at preventing infection and severe cases — is recommended for children between 12 and 15 months old for the first shot, with the second coming between 4 and 6 years old.
The vaccine series is required for kids before entering kindergarten in public schools nationwide.
According to CDPH, Chicago has a high measles, mumps and rubella vaccination rate, "meaning that most children and adults in Chicago are vaccinated and protected."
"Illinois children as young as 7 years-old can get vaccinated at pharmacies under Illinois law," according to the department. "CDPH Immunization clinics provide MMR vaccine for no out-of-pocket cost to any child 0–18 years and uninsured adults 19 and older."
According to CDPH, individuals who are traveling out of the country, including children over the age of 6 months, should talk to their healthcare provider about whether an additional dose of MMR vaccine is recommended before travel.
"People who are frequently around international travelers, such as individuals who work at airports or taxi and rideshare drivers, should also be sure to double check their vaccination status, as their risk of exposure to measles is heightened," CPDH said.
If you don’t know if you've been vaccinated, you can check the Illinois Immunization here.
"If you were vaccinated before 1968, check with your healthcare provider about a revaccination," the Cook County Department of Public Health said. "A blood test can confirm if you still have immunity. Talk to your healthcare provider if you’re unsure."
Editor's Note: The CCPH originally listed Chicago Public Library – Independence Branch, at 4024 N. Elston Ave., as a place of potential exposure. CCPH clarified Thursday that the patient did not visit that library branch, and that it is no longer considered a measles exposure location.
