As of October 1, 2026, the CDC has confirmed 3,887 measles cases nationwide, already exceeding the full-year 2025 total of 2,289 and marking the highest annual count since 1991. Weekly additions of 170–230 cases continue amid 42 outbreaks, with 95% of infections outbreak-associated and 95% occurring in unvaccinated or unknown-status individuals. Pennsylvania leads with nearly 1,000 cases, alongside major activity in South Carolina, Utah, and other jurisdictions spanning 47 states. Declining kindergarten MMR coverage below the 95% herd-immunity threshold in localized pockets sustains transmission following importations. CDC updates arrive weekly, with the Pan American Health Organization scheduled to review U.S. elimination status in November.