Measles cases in the United States have climbed past the 2025 total of 2,289 cases, reaching 2,318 reported cases as of Thursday, according to the Centers for Disease Control and Prevention. This marks the nation’s worst year for measles since 1991, driven by major outbreaks in South Carolina, Utah, and Arizona along with smaller clusters in other states. With several months still remaining in 2026, health officials project the year could significantly exceed current case counts.
The resurgence reflects declining vaccination coverage across the country. The national vaccination rate for measles, mumps, and rubella among kindergarteners dropped to 92.5% during the 2024-25 school year from 95.2% in 2019-20. Public health experts maintain that a 95% vaccination threshold is necessary to prevent outbreaks. The United States achieved measles elimination in 2000 through sustained high vaccination rates, but declining protection has created conditions for spreading. International health officials will convene in November to assess whether the United States and Mexico have lost their measles-free status.
Actual case numbers are believed to significantly undercount the true outbreak scope. In Utah, where the outbreak has lasted over a year, state epidemiologists estimate the true number of cases could be three to four times higher than the reported 700. South Carolina’s outbreak of 997 cases is acknowledged by state health officials as incomplete, though officials cannot quantify the undercount. Mathematical modeling of Texas’s 2025 outbreak suggests it may have been nearly twice the size of the 762 confirmed cases. Officials cite multiple factors contributing to undercounting, including people who become ill but do not seek testing, incomplete household contact information, and limited disease surveillance in certain communities.
Experts attribute the incomplete reporting to structural gaps in disease surveillance. Hospitalization data, which could serve as a proxy for measuring outbreak severity, are not uniformly reported across all states. Researchers working on outbreak analyses note that by the time health officials identify three linked cases—the CDC’s definition of an outbreak—substantial community transmission may already have occurred in low-vaccination areas. Texas state epidemiologists acknowledged instances where individuals tested positive for measles but contact information remained incomplete.
Public health officials emphasize that prevention through vaccination remains the primary control measure. State epidemiologists note that once measles circulates in communities with insufficient vaccination coverage, mitigation options become extremely limited. Certain populations remain particularly vulnerable, including infants too young for vaccination, immunocompromised individuals, and those who do not develop robust immunity from vaccines.
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