As of early October 2026, the United States has recorded 3,887 confirmed measles cases—already exceeding the full-year 2025 total of 2,289 and marking the highest annual count since 1991—driven primarily by sustained outbreaks in communities with low MMR vaccination coverage and record kindergarten exemption rates of 4.2%. CDC data show 95% of 2026 cases linked to 42 outbreaks, with 93-95% occurring in unvaccinated or unknown-status individuals and 9% requiring hospitalization. The virus's extreme contagiousness (roughly 90% secondary attack rate among susceptible contacts) has enabled rapid spread from imported and lingering 2025 clusters, particularly in Pennsylvania, South Carolina, and Utah. Weekly CDC surveillance reports through year-end, alongside state-level updates on case counts and vaccination trends, remain the key near-term data releases that could shift market-implied odds on final totals.