As of September 24, 2026, the CDC has confirmed 3,659 measles cases across 47 U.S. jurisdictions, with recent weekly additions near 188 amid ongoing outbreaks tied to pockets of low MMR vaccination coverage. Measles’ basic reproduction number of 12–18 enables rapid spread in susceptible communities, and 2026 totals already far exceed prior years. From late September through October 31, continued transmission at current rates would add several hundred more cases before the market resolves. CDC surveillance updates and state health department reports on new clusters or hospitalizations remain the key near-term data points that could shift trader assessments of final cumulative counts.