Overview
- Kane County confirmed the second measles case on Wednesday, Sept. 9, and health officials say the new patient was vaccinated and had been a known contact of an unvaccinated index case from August.
- The first case was infectious while attending Kaneland High School on Aug. 18 and was at Next Generation Pediatric Clinic on Aug. 24, creating nearly 1,600 potential exposures that triggered contact tracing.
- Unvaccinated people who were exposed remain under a 21-day quarantine and vaccinated contacts are being told to monitor for symptoms for up to 21 days after exposure.
- Officials emphasize the MMR vaccine strongly reduces severe illness and lowers transmission risk even though rare breakthrough infections can occur, and they are reaching out directly to known contacts of the new case.
- Public-health leaders link the cluster to a wider 2026 U.S. measles resurgence, including a separate outbreak in southwestern Wisconsin, and say vaccination and quick contact tracing are the best tools to limit spread.