The number of measles cases in the U.S. just hit a 35-year high - with 2,295 cases reported nationwide in 2026.

That’s nearly 200 more cases than the 2,126 tracked following an outbreak in 1991, according to new data from the Johns Hopkins Bloomberg School of Public Health, and just above last year’s 2,289 total.

The uptick is tied to vaccine hesitancy in certain communities that has allowed the life-threatening virus to circulate more widely, the school’s experts say.

Infections can lead to brain swelling, pneumonia, fever, ear infections and a rash - but taking the measles-mumps-rubella vaccine can prevent illness.

“High vaccination coverage has protected even the un- and undervaccinated because of herd protection, keeping measles at bay for the past few decades,” the school’s International Vaccine Access Center Executive Director Dr. William Moss explained in a statement. “But in communities with pockets of susceptible individuals across a broad age range, measles has been able to take hold, infecting those who are susceptible and spreading rapidly.”

Nearly all of the confirmed cases were in individuals who were unvaccinated or under-vaccinated and many were in young children, for whom infections may be more severe, data from the Centers for Disease Control and Prevention shows.

Federal data has not yet recorded as many cases, reporting 2,260 a week ago. The school’s tracker was last updated on Wednesday.

”CDC is aware of probable measles cases being reported by jurisdictions. However, the data on this page only includes confirmed cases jurisdictions have notified to CDC,” the agency said.

Outbreaks have ballooned across South Carolina, Utah, Texas and Virginia this year, with cases spreading in religious communities, grocery stores and schools.

The largest outbreak in northern South Carolina, with 997 cases, ended in April due to what Dr. Edward Simmer, the interim director of the state’s health department, said was a “textbook response,” according to NPR.

That included more people getting the vaccine - a factor in ending the outbreak in West Texas in 2025.

But Dr. Brannon Traxler, the health department’s Chief Medical Officer, cautioned that risks remain in areas with low vaccination rates.

“If we don’t continue to see increases in vaccination, I’m worried that we could see another large … outbreak in a community where it gets introduced from someone who traveled,” she said in a statement shared by the American Academy of Pediatrics.

There’s a similar concern nationally. Most states are below the threshold needed for community immunity among kindergarteners, a CDC map shows. That’s why getting vaccinated is so important, Moss added.

“Measles vaccines are extremely safe and effective,” he said. “Getting you or your child vaccinated is the best way to protect against disease.”

Measles vaccines helped the U.S. eliminate measles 26 years ago.

The recent surge of cases has threatened America’s longstanding elimination status, which indicates there has not been continuous spread of the infectious disease for more than a year. A meeting will be held to decide if that status has been lost in November.