As of October 8, 2026, the CDC confirmed 4,080 measles cases nationwide, already far exceeding 2025’s full-year total of 2,289 and the highest annual count since 1991. Primary drivers include 42 active outbreaks accounting for 96% of cases, with sustained domestic transmission concentrated in under-vaccinated communities—95% of patients are unvaccinated or have unknown status. Pennsylvania leads with over 1,100 cases, followed by notable activity in South Carolina, Utah, and Wisconsin; weekly additions averaged roughly 190 cases recently. CDC surveillance updates, state health department reports, and any new outbreak declarations remain key near-term data points that could influence market-implied odds through October 31.