Show summary Hide summary
Illinois health officials have confirmed a handful of measles cases this year and traced possible exposures at churches, retail stores and O’Hare Airport, raising fresh questions about transmission in public spaces even as statewide school vaccination rates hover at the level experts say prevents large outbreaks. The timing — following a nationwide spike in measles in 2025 — makes the state’s immunization coverage a key factor in whether these isolated cases remain contained.
Recent cases and where people may have been exposed
State and county public health agencies logged the first reported measles incident in 2026 on Feb. 16, tied to a church event in Collinsville with a likely exposure on Feb. 8. Officials later confirmed a case in DeKalb County announced March 12, with investigators tracing possible contact at a local Walmart and a post office.
Camden Lazenby: what to know about the story making headlines today
NHL playoffs expansion: devalues the regular season and rewards mediocrity
On March 31, Cook County Health issued alerts after identifying possible exposures at multiple Chicago-area locations, including O’Hare International Airport and two Niles businesses — a grocery store and a Marshalls outlet. Investigators say the person believed to have been contagious also visited an urgent care clinic in Mt. Prospect days earlier.
Local health departments continue routine contact tracing to identify and notify anyone who might have been exposed. DeKalb County officials reported that tracing efforts are ongoing and, so far, no unusual transmission chains have been detected.
Why this matters now
After the United States recorded its worst measles season in decades in 2025, even single cases can trigger public concern because measles spreads very efficiently in crowded settings. Experts say community immunity is the strongest defense; when coverage slips below recommended levels, the risk of larger outbreaks rises quickly.
How contagious is measles?
Measles ranks among the most easily transmitted infectious diseases. The virus travels through the air in respiratory droplets and can remain infectious in an enclosed space for hours after an infected person leaves.
The Centers for Disease Control and Prevention estimates substantial risk for unvaccinated people: roughly one in five who contract measles in the U.S. require hospitalization, about one in 20 children with measles develop pneumonia, and roughly one to three per 1,000 infected children die from respiratory or neurological complications. Encephalitis — inflammation of the brain — is a rare but serious outcome that can cause long-term disability.
Symptoms and when someone is contagious
Measles typically starts with fever, cough, runny nose and red or watery eyes; a distinctive reddish rash usually follows and spreads from the face downward. The disease can be mistaken for influenza early on, but the rash and the pattern of symptom progression help clinicians distinguish measles from the flu.
- Key symptoms: high fever (often above 101°F), persistent cough, runny nose, conjunctivitis, and the spreading rash.
- Contagious period: people are infectious from about four days before the rash appears through four days after the rash starts.
Anyone who suspects they may have measles should contact their healthcare provider in advance of visiting a clinic or emergency room so staff can arrange care that limits exposure to others.
Who is most at risk?
Infants under 12 months, young children, adults over 20, pregnant people who are not immune, and individuals with weakened immune systems face the greatest danger from measles. Public health officials emphasize that the highest concern is for those who are unvaccinated.
The role of vaccination
The most effective protection is the measles vaccine delivered as part of the MMR vaccine (measles, mumps, rubella). Illinois school-entry data indicate that more than 95% of students have received the recommended doses — a level the CDC cites as the minimum needed to maintain herd immunity and prevent outbreaks.
Routine schedule in the U.S.:
- First dose at 12–15 months of age
- Second dose at 4–6 years
Illinois requires one MMR dose for most childcare attendance and two doses for kindergarten through 12th grade. Health officials note infants younger than 12 months remain vulnerable because they are not yet eligible for routine vaccination.
What to do if you think you were exposed
If you believe you may have been exposed to measles, public health guidance is straightforward: check your vaccination records, call your healthcare provider, and notify your local health department. Providers typically ask symptomatic patients to call ahead so clinics can take precautions to reduce further spread.
- If you’re unvaccinated: talk to your clinician about getting the MMR vaccine as soon as possible; vaccination can prevent or reduce illness if given before symptoms develop.
- If you’re symptomatic: stay home, except to seek medical care, and follow directions from public health officials.
- Pregnant people and infants: contact your provider immediately if exposure is suspected.
Local immunization levels
State tracking of school-based immunization shows most Illinois counties meet or exceed the threshold believed to prevent widespread transmission. Below is the most recent county-level snapshot reported by the Illinois Department of Public Health.
| County | Percent of school-aged children immunized |
|---|---|
| DeKalb | 96.8% |
| McHenry | 95.7% |
| Kane | 95.6% |
| Kendall | 96.3% |
| Kankakee | 94.7% |
| DuPage | 95.9% |
| Will | 96.3% |
| La Salle | 97.0% |
| Ogle | 95.2% |
| Lee | 96.7% |
| Bureau | 95.5% |
| Putnam | 97.3% |
| Whiteside | 96.6% |
| Grundy | 92.4% |
| Lake | 95.5% |
Maintaining or improving these coverage levels is critical to keep occasional cases from becoming community-wide outbreaks. Public health teams continue monitoring, notifying exposed individuals, and urging eligible people to verify their immunization status.
