Measles Cases Reach 35-Year High, Threatening US Elimination Status

The United States has recorded more confirmed measles cases in 2026 than in any year since the disease was declared eliminated from the country in 2000, according to data the Centers for Disease Control and Prevention updated on Thursday. The tally, 3,134 confirmed cases so far this year, surpasses the previous 35-year high set only last year and comes as an international commission prepares to decide within weeks whether the country has lost its elimination status altogether.

The milestone lands amid an unusual public dispute. Pennsylvania health officials attributed two deaths in Lancaster County to measles in late August, the state's first fatalities from the disease in more than three decades, only for Health and Human Services Secretary Robert F. Kennedy Jr. to question on social media whether the deaths were accurately linked to the virus. The CDC's national count has not yet incorporated those two 2026 deaths while the agency reviews the cases, even as state officials say their epidemiologists have confirmed both individuals tested positive for measles.

The numbers

Of the 3,134 cases reported in 47 jurisdictions, 3,118 were among U.S. residents and 16 were linked to international visitors, the CDC's tracker shows. Ninety-five percent of this year's cases, or 2,969, are tied to one of 38 outbreaks recorded so far in 2026, and the large majority of patients were unvaccinated or had no documented vaccination history. Pennsylvania has borne the brunt of the recent surge, with case counts climbing by more than 100 in a single week in late August, according to state figures, while Wisconsin and Ohio have also reported fast-growing clusters over the same period.

Those numbers sit against a backdrop of eroding childhood immunization rates. National kindergarten vaccination coverage data published by the CDC last month show that measles, mumps and rubella vaccine coverage among incoming kindergartners fell to 92.4% in the 2025-26 school year, down from 95.2% in 2019-20, the last school year before the pandemic. Exemptions from one or more required vaccines rose to 4.2% of kindergartners nationally, up from 3.6% the prior year, with 24 states now reporting exemption rates above 5%. Roughly 280,000 kindergartners started the school year without documentation of a completed MMR series.

How the country got here

Measles was declared eliminated in the United States in 2000, meaning the virus no longer circulated continuously within the country for 12 months or more, though travelers have continued to import cases from abroad ever since. Maintaining that status depends on stopping any single imported strain from spreading for a full year. The Pan American Health Organization's regional elimination commission, which verifies elimination status for countries across the Americas, postponed its scheduled review earlier this year and is now due to make its determination in November.

An analysis published in The Lancet concluded that the country has already failed to meet four of the seven epidemiological benchmarks used to confirm elimination and is unlikely to satisfy the remaining three before the commission convenes, making a loss of status "highly likely." The vaccination declines tracked by the CDC since the pandemic, concentrated in communities with religious or personal exemptions, are widely cited by public health researchers as the principal driver, since sustained herd immunity against measles requires coverage at or above 95%, a threshold the country has not met nationally since before COVID-19.

The current surge is not unique to the United States. Measles cases have also risen sharply across parts of Europe and in Canada in recent years, driven by similar drops in routine childhood vaccination following pandemic-era disruptions to primary care and a parallel rise in vaccine hesitancy. What distinguishes the U.S. outbreak, researchers say, is the length and geographic breadth of continuous domestic transmission, which is the specific technical measure the regional commission uses to decide whether elimination has genuinely been lost, as opposed to a temporary spike in imported cases.

The burden of this year's outbreaks has fallen heavily on young children and on close-knit communities with lower vaccination rates, including Amish and Mennonite populations in parts of Pennsylvania. State officials said one of the two Pennsylvania deaths was a six-week-old infant with an underlying genetic condition and the other involved a baby born prematurely after the mother went into labor early while infected. Health officials have repeatedly noted that infants too young to be vaccinated, pregnant women and people who are immunocompromised face the highest risk of severe complications, including pneumonia and encephalitis. The CDC's clinical guidance for measles estimates that one to three of every 1,000 children infected will die from respiratory or neurologic complications, and notes that even previously healthy children can require hospitalization.

Beyond Pennsylvania, families in Wisconsin, Ohio and other states with active outbreaks are being urged to check their children's vaccination records now that the school year is underway nationwide, since even brief exposure in a classroom, waiting room or place of worship can spread the virus among unvaccinated children. A loss of elimination status would not change how the disease is treated but would mark a symbolic and scientific setback, undoing the very achievement the 2000 declaration was meant to protect, and could affect how international health bodies classify travel risk to and from the United States.

Reaction

Pennsylvania's health secretary, Dr. Debra Bogen, said in the department's announcement of the deaths that residents' unfamiliarity with the disease compounds the danger.

"My deepest sympathies are with the loved ones who are facing this unimaginable loss. Because measles was largely eliminated in the Commonwealth for more than three decades, people are not familiar with this disease and don't fully understand the potential severity of the illness."

Kennedy has suggested on social media that the Pennsylvania deaths "may even have been altogether fabricated," touching off a public dispute over the death toll that Bogen's department has rejected, saying its epidemiology team "thoroughly investigated and verified" that both people who died had tested positive for measles. Pennsylvania Governor Josh Shapiro has said Kennedy's rhetoric undermines public confidence in vaccines at a time when the state is trying to contain active transmission.

Dr. Demetre Daskalakis, who directed the CDC's immunization center before resigning last year, said the pattern of continuous spread has changed the character of the outbreak. "Measles is acting like it's endemic now," he said. "There's a lot of domestic transmission." Dr. William Moss of Johns Hopkins University said regaining elimination status, if it is lost, would not be simple. "Getting it back would take a tremendous amount of work," he said. "We would have to stop measles virus transmission in the country."

What happens next

The Pan American Health Organization's verification commission is expected to issue its determination in November, based on whether genomic sequencing shows the virus circulating in Pennsylvania and other outbreak states descends from a single uninterrupted chain of transmission reaching back roughly a year. The CDC has said it will continue to update its national case count, including its review of the two Pennsylvania deaths, as additional information becomes available.

With the school year now underway across most of the country, state and local health departments are focused on the more immediate task of containing active clusters before they seed new ones elsewhere. Public health officials have urged parents who are unsure of their children's vaccination status to consult a pediatrician, noting that two doses of the MMR vaccine are about 97% effective at preventing infection, and that a single additional dose can often be added to a child's existing school-immunization record within days.