Ongoing measles transmission in the United States, driven by persistent outbreaks in under-vaccinated communities and continued importation via international travel, has produced 1,842 confirmed cases as of May 7, 2026, according to CDC surveillance. Most cases remain outbreak-associated, with 93 percent linked to clusters that originated in late 2025, particularly in South Carolina and Utah, where the highly contagious virus (basic reproduction number 12–18) spreads rapidly among individuals lacking two doses of MMR vaccine. Recent weekly increments have slowed from double-digit percentage gains earlier in the year to under 1 percent, yet summer travel and school-related mixing could accelerate spread. CDC releases updated case counts each Thursday, while the November review of U.S. measles elimination status—last achieved in 2000—will hinge on whether sustained domestic transmission exceeds one full year.