As of mid-September 2026, the CDC has confirmed 3,471 measles cases nationwide—already exceeding the full-year 2025 total of 2,289—with weekly additions exceeding 170 cases and 39 active outbreaks driving most transmissions. Over 95% of cases involve unvaccinated or unknown-status individuals, concentrated in school-age groups, amid declining MMR coverage that leaves clusters vulnerable to the virus's high R0. Large ongoing outbreaks, particularly in Pennsylvania (hundreds of cases and multiple reported deaths under investigation), South Carolina, Utah, and Texas, account for the majority, with 9% hospitalization rates observed so far. CDC weekly surveillance updates and state health department reports remain the key data releases that could shift market-implied probabilities through the final months of the year.