Sustained measles transmission across 47 U.S. jurisdictions, fueled by low MMR vaccination coverage and record-high nonmedical exemptions among kindergartners, has driven the 2026 case count to 3,659 confirmed infections as of September 24 per CDC data. This total already exceeds all prior years since elimination in 2000, with 95% of cases unvaccinated or unknown status, 40 active outbreaks, and 95% outbreak-linked, including chains persisting from 2025. Pennsylvania leads with over 850 cases amid ongoing local spread. Official CDC counts remain preliminary and subject to revision through the end of the month, while an international review of elimination status is scheduled for November. Traders should monitor final weekly CDC updates for any late-September additions that could shift market-implied odds.