Sustained measles transmission across multiple states continues to shape trader expectations for total U.S. cases by May 31, driven primarily by ongoing outbreaks in under-vaccinated communities. As of the CDC’s May 8 update, 1,842 confirmed cases have been reported in 2026, with 93% linked to outbreaks and 92% occurring among individuals who are unvaccinated or whose status is unknown. The largest clusters remain concentrated in South Carolina, Utah, and Texas, where low MMR coverage has enabled sustained local spread since late 2025. Weekly case additions have slowed recently, suggesting possible deceleration, yet new detections in additional jurisdictions could still push totals higher before month-end. CDC surveillance updates and state health department reports through late May represent the key data releases likely to move market-implied odds.