Case 1
The first case was a Kane County resident who was unvaccinated against measles and had recently traveled internationally. The case was confirmed in August 2026.
KCHD identified locations where individuals may have been exposed and worked with healthcare providers, schools, community partners and the Illinois Department of Public Health (IDPH) to identify and notify people who may have been exposed.
The individual was no longer infectious as of August 25, 2026.
The first case resulted in up to 1,600 potential exposures, requiring KCHD to identify and notify people who may have been exposed and provide guidance to help prevent further spread.
Case 1 Potential Exposure Locations
- Kaneland High School, 47W326 Keslinger Road, Maple Park, IL 60151, August 18, 2026 – all day
- Next Generation Pediatric Clinic, 107 S. McLean Blvd., Suite B, South Elgin, IL 60177, August 21, 2026 – 12:30 p.m. to 4 p.m.
Case 2
KCHD is investigating a second confirmed case of measles in a vaccinated individual who was a contact of the first case and is also no longer infectious.
While the measles, mumps and rubella (MMR) vaccine provides strong protection against measles, breakthrough infections can occur. People who are vaccinated and develop measles are generally less likely to experience severe illness or complications and may be less likely to transmit the virus.
KCHD is identifying people who may have been exposed to the second case and is contacting known contacts to provide guidance. Identification of contacts is ongoing, and not all contacts have been contacted yet.
If you are identified as a contact of the second case, KCHD will provide specific instructions based on your exposure and vaccination status.
If You Were Potentially Exposed
Being exposed to measles does not mean that you have measles. Depending on your vaccination status and individual circumstances, you may be asked to monitor for symptoms, provide documentation of immunity or quarantine.
If You Were Potentially Exposed and Are Vaccinated
People who are vaccinated against measles should monitor themselves for symptoms for 21 days after their last potential exposure.
Symptoms of measles may include:
- High fever
- Cough
- Runny nose
- Red, watery eyes
- A rash that generally appears 3-5 days after the first symptoms and typically begins on the face and spreads to the rest of the body
If you develop symptoms:
- Stay home.
- Call your healthcare provider before going to a medical facility.
- Tell your healthcare provider that you may have been exposed to measles.
- Follow the instructions provided by your healthcare provider.
Do not go directly to an emergency department, urgent care or other healthcare facility without calling ahead. Measles is highly contagious, and arriving without advance notice could expose other patients and healthcare workers.
If you remain symptom-free through the end of the 21-day monitoring period, you do not need to take further action related to that exposure.
If You Were Potentially Exposed and Are Unvaccinated
Individuals who were unvaccinated and potentially exposed to Case 1 have been contacted directly by KCHD and were already under quarantine.
If you are already under quarantine because of potential exposure to Case 1, continue following the quarantine instructions provided by KCHD. This new case does not change your quarantine instructions unless KCHD contacts you directly.
KCHD is currently reaching out to individuals who were contacts of Case 2 to provide quarantine guidance. Specific instructions will be based on the individual's exposure and vaccination status.
If you have been contacted by KCHD regarding a measles exposure, follow the instructions provided by KCHD.
What Are the Symptoms of Measles?
Measles is a highly contagious respiratory illness.
Symptoms may include:
- High fever
- Cough
- Runny nose
- Red, watery eyes
- Rash that generally appears 3-5 days following other symptoms and typically begins on the face and spreads to the rest of the body.
If you develop symptoms and think you may have been exposed to measles, stay home and call your healthcare provider before going to a medical facility. Tell the provider that you may have been exposed to measles so they can provide instructions and help prevent exposure to others.
Do not arrive at an emergency department, urgent care or other healthcare facility without calling ahead.
Measles Infection After Vaccination
The MMR vaccine is highly effective at preventing measles, but no vaccine provides 100% protection.
In a small percentage of cases, a person who has received the recommended doses of MMR can develop a breakthrough infection after being exposed to measles.
A breakthrough case does not mean that the vaccine did not work. Two doses of MMR vaccine provide approximately 97% protection against measles, and vaccination remains the best way to prevent measles and its complications.
People who develop measles despite vaccination generally have milder illness, are less likely to experience complications and are less likely to spread the virus to others.
Protect Yourself and Your Community
The best protection against measles is vaccination. Two doses of MMR vaccine provide the strongest protection and are highly effective at preventing measles.
Need an MMR Vaccine?
If you need the MMR vaccine for yourself or a family member, you can contact:
Can't Find Your Vaccination Records?
If you are unsure whether you have received the recommended doses of MMR, check your immunization records or contact your healthcare provider.
If you cannot locate your vaccination records, you can contact:
Your healthcare provider can discuss whether vaccination or blood testing is appropriate.
Why Vaccination Matters
The first measles case in Kane County this year demonstrated how quickly measles can create a significant public health response. That individual had up to 1,600 potential exposures, requiring KCHD to identify and notify people who may have been exposed and provide guidance to help prevent further spread.
The second case also highlights an important point about measles vaccination: vaccination greatly reduces the risk of getting measles, but breakthrough infections can occur. Even when a vaccinated person develops measles, vaccination generally provides protection against severe illness and complications.
Vaccination remains our strongest tool for preventing measles and limiting its spread. Everyone who may have been exposed, regardless of vaccination status, should take potential exposure seriously, monitor for symptoms and follow guidance from public health officials.
KCHD thanks the individuals who followed quarantine guidance after the first case. Their cooperation and willingness to stay home during the monitoring period helped reduce opportunities for measles to spread in our community.
Measles Activity in Southwestern Wisconsin
Kane County residents should also be aware of an ongoing measles outbreak in southwestern Wisconsin.
As of September 8, 2026, the Wisconsin Department of Health Services reports 151 confirmed and six probable measles cases in Grant, Iowa and Lafayette counties. Public health officials report that measles continues to spread locally in the area.
Southwestern Wisconsin is a popular destination for visitors from northern Illinois, including during the Labor Day holiday weekend. People who recently traveled to the area may have spent time in communities where measles is currently spreading.
KCHD encourages residents who traveled to southwestern Wisconsin to be aware of the ongoing outbreak and to monitor for symptoms of measles, particularly if they are not vaccinated or are unsure of their vaccination status.
