It鈥檚 been a year since a measles outbreak began in West Texas, and international health authorities say they plan to meet in April to determine if the U.S. has lost its measles-free designation.
Experts fear the vaccine-preventable virus has regained a foothold and that the U.S. in losing the achievement of having eliminated it.
The reevaluation is largely symbolic and hinges on whether a single measles chain has spread uninterrupted within the U.S. for at least 12 months.
Public health scientists around the country are investigating whether the now-ended Texas outbreak is linked to active ones in Utah, Arizona and South Carolina. But doctors and scientists say the U.S. 鈥� and North America overall 鈥� has a measles problem, regardless of the decision.
鈥淚t is really a question of semantics,鈥� said Dr. Jonathan Temte, a Wisconsin family physician who helped certify the U.S. was measles-free in 2000. 鈥淭he bottom line is the conditions are sufficient to allow this many cases to occur. And that gets back to de-emphasizing a safe and effective vaccine.鈥�
Last year, the Centers for Disease Control and Prevention confirmed 2,242 measles cases across 44 states 鈥� 鈥� and nearly 50 separate outbreaks.
The problem has been years in the making, as get routine vaccines due to parental waivers, health care access issues and rampant disinformation. More recently, Trump administration health officials including Health Secretary have and about the established safety of vaccines at an unprecedented level while also to improve vaccination rates.
鈥淭he most important thing that we can do is to make sure the people who aren鈥檛 vaccinated get vaccinated,鈥� said Jennifer Nuzzo, director of Brown University鈥檚 Pandemic Center. 鈥淲e have not issued a clear enough message about that.鈥�
A Department of Health and Human Services spokesperson said Thursday that Kennedy has emphasized vaccines as the best way to prevent measles, adding that the CDC is responding to outbreaks and working to increase vaccination rates.
In a briefing Tuesday, department officials said they don’t yet have evidence that a single chain of measles has spread for a year.
But CDC鈥檚 principal deputy director said he would consider the loss of elimination status to be the 鈥渃ost of doing business” globally.
鈥淲e have these communities that choose to be unvaccinated,” said Dr. Ralph Abraham. 鈥淭hat’s their personal freedom.鈥�
Measles finds the unvaccinated
There is little room for error in trying to stop measles. The virus is one of the most contagious, infecting 9 out of every 10 unvaccinated people exposed. Community-level protection takes a 95% vaccination rate. The current rate nationally is 92.5%, according to CDC data, but many communities fall far below that.
The patient in Texas鈥� first known case developed the telltale rash on Jan. 20, 2025, according to state health department data.
From there, the outbreak exploded. Officially, 762 people fell ill, most of them in , and two children died. Many more got sick and were never diagnosed: 182 potential measles cases among children in Gaines County went unconfirmed in March 2025 alone, state health officials said, a possible undercount of 44% in that county.
Such data gaps are common, though, making it especially hard to track outbreaks. Many people living in communities where the virus is spreading face barriers, including access to health care and distrust of the government.
Contact tracing so many cases is also expensive, said behavioral scientist Noel Brewer, who chairs the U.S. committee that will finalize the data for international health officials. Research shows can cost public health departments .
CDC data on measles is still among the best worldwide, Brewer said, but 鈥渢he U.S. has changed its investment in public health, so we鈥檙e less able to do the case tracking that we used to do.鈥�
Genetic sequencing can fill some gaps.
Scientists have confirmed the same measles strain in Texas, New Mexico, Utah, Arizona, South Carolina, Canada, Mexico and several other North American countries, said Sebastian Oliel, a spokesperson for the Pan American Health Organization, which plans to make the final decision on U.S. measles elimination at an April 13 meeting.
But that’s not always enough to say the outbreaks are connected. Genetically, the measles virus doesn’t change as often as, say, flu.
鈥淲ithin an outbreak, everybody is going to look the same,鈥� said Justin Lessler, a University of North Carolina disease researcher.
The key question may then be how PAHO experts will navigate final data gaps, said Dr. Andrew Pavia, a Utah physician and longtime CDC consultant.
鈥淢y best guess is we will lose elimination status,鈥� Pavia said. 鈥淭he case for this not being continuous transmission is tenuous, and I think they are likely to err on the side of declaring it a loss of elimination status.鈥�
Oliel said when there is a case of unknown origin in a country with ongoing local spread, 鈥渢he most conservative approach is to consider the case part of the existing national transmission.鈥�
Mexico also up for review
PAHO will review Mexico’s measles-free status alongside the U.S., Oliel said. The country’s largest outbreak has roots in Texas. It started when an 8-year-old boy from Chihuahua state got sick after visiting family in Seminole, Texas. Since last February, 6,000 people have gotten sick in Mexico, and 21 have died in Chihuahua state.
But under PAHO’s definition of elimination, borders matter. If, for example, the chain of measles that started in the U.S. spread to Mexico and then returned to the U.S. anew, it would be considered a new chain, experts said. Still, many experts call that standard outdated.
What’s clear is that measles found ample ground in the U.S. in 2025, infiltrating and day cares, churches, hospital waiting rooms and . New Mexico logged 100 cases and . Kansas officials spent seven months trying to control an outbreak that sickened nearly 90 people across 10 counties. Ohio confirmed 40 cases. Montana, North Dakota and Wisconsin each had 36.
Now, more than 800 people have gotten sick across Utah, Arizona and South Carolina since late summer, .
鈥�2025 was the year of measles,鈥� Brewer said. 鈥淲ill 2026 be the year of rising or falling measles cases? Does it get worse or does it get better? No one knows the answer.鈥�
___
The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute鈥檚 Science and Educational Media Group and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.
Copyright © 2026 The Associated Press. All rights reserved. This material may not be published, broadcast, written or redistributed.
