ATLANTA — The United States has hit a grim new milestone in its ongoing measles crisis: the total number of cases recorded so far in 2026 has already eclipsed the full-year count from 2025 — and there are still five months left to go.
The U.S. Centers for Disease Control and Prevention reported 2,318 confirmed measles cases as of last Thursday, according to a Friday update from the agency. That figure tops the 2,289 cases tallied throughout all of 2025, which had already been the nation’s worst year for the disease in more than three decades.
With major outbreaks spreading across South Carolina, Utah, and Arizona — plus smaller clusters erupting in other states — 2026 has now become the worst year for measles in the U.S. since 1991.
The situation could have international consequences as well. This November, global health officials are scheduled to meet and decide whether the U.S. and Mexico have lost their measles-free designation. The U.S. had eliminated local measles transmission in 2000 by keeping vaccination rates high, but those rates have slipped below the 95% threshold needed to keep outbreaks at bay.
Even the alarming case counts may not tell the full story. Public health experts and disease researchers have long recognized that official tallies fall short of the true number, since many sick people never seek medical care. This isn’t a problem unique to measles — it affects tracking of many illnesses.
Experts say the actual spread could be significantly wider than reported figures suggest. The measles virus is among the most contagious pathogens known to science, and declining vaccination rates are making communities more vulnerable. Nationally, the measles, mumps, and rubella vaccination rate among kindergartners dropped to 92.5% in the 2024-25 school year, down from 95.2% in 2019-20. Experts note that even those averages can hide pockets of communities where coverage is far lower.
In Utah, public health officials have been battling a measles outbreak for more than a year. The state health department reports that more than 700 people have been infected during that span. Mathematical modeling and genetic analysis suggest the outbreak near the Utah-Arizona border could actually be three to four times larger than confirmed numbers indicate, according to state epidemiologist Dr. Leisha Nolen.
South Carolina’s situation is similarly hard to pin down. The state experienced the largest measles outbreak in 35 years, with a reported total of 997 cases — a number the state health department acknowledges is likely an undercount, though officials say they don’t know by how much.
Dr. Brannon Traxler, acting director of the state health department, said the gap between actual and reported cases is “impossible to know and may vary during the course of an outbreak.”
The lack of consistent data makes it difficult to gauge the true scale of any outbreak. Hospitalization rates can serve as a useful indicator, experts say, but not every state is required to report measles hospitalizations.
“If we really had some kind of solid gold standard for the percentage of all cases that have hospitalization or some measure of severity, then that would be another way of estimating the outbreak size that we could see if it’s consistent with these other methods,” said Damon Toth, an applied mathematician at the University of Utah’s medical school who is involved in one of the Utah outbreak analyses.
In Texas, researchers are still working to assess the full scope of last year’s outbreak. Early findings suggest it may have been nearly double the 762 cases that were officially confirmed.
Rémy Pasco, a mathematical epidemiologist at the University of Colorado Boulder who is contributing to that analysis, said undercounts were not surprising. Without sufficient community vaccination rates — which health experts set at 95% — “there’s just not much you can do about measles once you have it,” he said. He also noted that by the time three linked cases are identified — the CDC’s threshold for declaring an outbreak — in communities with low vaccination rates and limited disease monitoring, “either you missed the previous ones or you’re going to have a lot more.”
Dr. Varun Shetty, Texas’ chief state epidemiologist, described situations where individuals tested positive but health officials were unable to determine who else in their household may have been exposed or sick.
“What we’re able to count and report is almost always an underestimate of what actually occurred, because it relies on people being willing to be able to get tested, to share information with healthcare providers and with public health,” Shetty said. “Sometimes that just doesn’t happen.”
Texas health officials previously disclosed that 182 probable measles cases among minors in Gaines County — the heart of the state’s outbreak — went unconfirmed in March 2025 due to insufficient information. The confirmed case total for that western Texas county throughout the entire outbreak stands at 414.
Shetty said he expects measles cases and outbreaks to continue as long as large numbers of people remain unvaccinated. “It’s really critical, not only for individual people, but for communities, to have high vaccination coverage,” he said.
Dr. Mark Roberts, retired director of the Public Health Dynamics Lab at the University of Pittsburgh School of Public Health, said his greatest concern is for what he calls “innocent bystanders” — people who cannot receive the vaccine, including very young infants, those with compromised immune systems, and a small number of individuals who don’t develop strong immunity even after vaccination. His team’s research shows these groups tend to bear the heaviest burden when outbreaks begin.
Roberts offered a pointed comparison for those who view skipping vaccination as a personal choice. “Not vaccinating your kid is like saying, ‘I don’t want my car to have brakes,’” he said. “Because it’s other people that you can hit. It’s not just you in your car. It’s other people.”
