Measles outbreaks in the United States have fluctuated significantly over recent decades, driven by vaccination rates, travel patterns, and public health infrastructure responses. This market asks whether cumulative confirmed measles cases in the U.S. will reach or exceed 5000 during the calendar year 2026. The Centers for Disease Control and Prevention (CDC) maintains comprehensive case reporting and disease surveillance, making the outcome definitively verifiable and resolvable at year-end. Currently trading at 39% YES odds, the market reflects trader assessment that such an outbreak would require substantial erosion of herd immunity or a major public health disruption. Historically, the pre-vaccine elimination era saw measles cases in the millions annually; modern outbreaks in the U.S. typically number in the hundreds to low thousands, though travel-related imports and local transmission chains can spike quickly during seasonal peaks. The 39% odds suggest traders view a 5000-case threshold as possible but not the base case—requiring either significant vaccine hesitancy expansion, a high-profile import event, or broader systemic public health challenges. Market volume and liquidity remain steady, indicating continued trader interest in disease-related prediction markets.