The United States recorded more measles cases in 2026 than in all of 2025, making this the country's worst year for the disease since 1991.
Federal data show 2026 has already surpassed all of last year's record total with five months remaining.
Federal surveillance data showed that 2026 measles cases had surpassed the full 2025 total with more than five months left in the year.
The 2026 count reached the highest annual level since 1991, extending a second consecutive record-setting year.
Large outbreaks in South Carolina, Utah and Arizona accounted for hundreds of infections, while smaller clusters appeared in other states.
The Centers for Disease Control and Prevention defines an outbreak as three or more epidemiologically linked cases.
Measles is an airborne viral disease that can cause high fever, pneumonia, brain inflammation and death.
The United States declared local measles transmission eliminated in 2000 after maintaining high population vaccination coverage.
Public-health authorities generally cite about 95 percent two-dose coverage as the level needed to prevent sustained spread in a community.
National and local coverage has fallen below that threshold in many places, leaving clusters of susceptible children and adults.
Confirmed case totals can lag illness because reports move from clinicians and laboratories through state and federal surveillance systems.
The evidence supports a bounded conclusion: The United States recorded more measles cases in 2026 than in all of 2025, making this the country's worst year for the disease since 1991. It does not resolve the remaining uncertainty because The national total is provisional, and states may revise case classifications or report more recent local counts. The factual horizon is therefore defined by Weekly CDC case and outbreak updates and Whether large state outbreaks are declared over or seed new transmission chains.
The current reporting limit is specific: The national total is provisional, and states may revise case classifications or report more recent local counts.
The next verifiable developments are Weekly CDC case and outbreak updates and Whether large state outbreaks are declared over or seed new transmission chains.