A measles outbreak crossed into Mexico from Texas. A larger tragedy followed

By Mary Beth Sheridan, CNN

Cuauhtemoc, Mexico (CNN) — It all started when a 9-year-old boy went with his parents to visit relatives in Seminole, Texas, early last year. After he returned home to Mexico, a red rash erupted on his skin. Within weeks, so many of his classmates fell ill that their school shut down.

Unbeknownst to the boy’s parents, measles had started to ricochet around Seminole during their visit.

The town would soon emerge as the epicenter of the biggest US outbreak in more than 30 years, one that would kill three Americans. But when the virus jumped the border to Mexico, a bigger tragedy was about to begin.

At least 40 Mexicans have died of measles complications since the start of 2025, ranging from babies to middle-age farmworkers, according to the Mexican Health Ministry. More than 17,000 infections have been confirmed in that period, four times the number in the United States. Measles is largely preventable with two shots of a common vaccine. But most of those with infections hadn’t gotten it.

Mexico’s ongoing measles outbreak offers a case study of what can happen when a country’s vaccine coverage slips. The disease was first identified in the 9-year-old’s neighborhood, in a secluded Mennonite community of apple, wheat and corn farms in Chihuahua state, south of Texas, authorities said. It spread to agricultural laborers, many of them from Indigenous communities.

By the end of 2025, this Mexican state, roughly the size of Michigan, had confirmed around 4,500 cases – more than in the entire United States.

Pinning down the movement of a microscopic pathogen can be difficult. But Mexican authorities believe that the measles virus probably arrived in the throat or lungs of the third-grader, who was unvaccinated, and then spread wildly.

From Canada to Mexico to Chihuahua

In Chihuahua, officials did genetic tests on more than 100 cases. Each came back with the stamp of the measles virus that popped up in Canada in 2024 and later appeared in Texas: genotype D8 and lineage MVs/Ontario.CAN/47.24. The virus has since traveled through Mexico’s 32 states.

“Everything comes from the outbreak in Chihuahua,” said Dr. Miguel Nakamura, director of epidemiological information at Mexico’s Health Ministry.

In the United States, a series of measles outbreaks starting in Seminole raised concerns about the growing role of vaccine skeptics in the government.

Mexico’s case is somewhat different. The president, Claudia Sheinbaum, is a leftist with a PhD in engineering who prides herself on her scientific background. What unites the neighboring nations’ outbreaks is something else, epidemiologists say: complacency.

Measles was declared eliminated in both countries more than a quarter-century ago – a historic public-health achievement. But Mexico’s once-robust vaccine program has atrophied amid disarray in its government-dominated health system, say epidemiologists.

“This is the paradox,” said Samuel Ponce de León, an epidemiology professor at the National Autonomous University of Mexico. Thanks to the success of vaccines, “you don’t see kids with signs of polio or complications from measles, like deafness or meningitis. We stopped having measles cases, so people began to say, ‘Why should I worry?’”

More contagious than Covid-19

Measles is one of the most contagious diseases in the world, far more so than Covid-19. It’s spread by an infected person coughing, sneezing or even just talking. The virus can hang in the air for up to two hours. A single person can potentially infect 18 others.

Many cases are mild. The 9-year-old who returned from Seminole developed a high fever and rash but quickly got better and returned to school, said his mother, who spoke with CNN on the condition of anonymity.

He lives at the edge of the city of Cuauhtemoc, in a community of around 30,000 Mennonites, a Protestant group known for their piety, hard work and pacifism. The boy’s mother contacted his school when he became ill, saying she thought he might have measles. The principal, Oscar Peters, told CNN that he then reached out to his own doctor, who advised him not to worry. Measles cases were rare.

A few days later, one of the boy’s Mennonite classmates, Artemio Bergen, an energetic tow-headed boy who loved riding his bike and reading horror stories, came down with a high fever. His parents watched helplessly as the boy lay prostrate, his body aflame; medicine provided no relief. Soon, red blotches were sprouting on his skin.

At that point, the family sent photos of the boy to his 87-year-old great-grandmother. She panicked. “Run, run to the hospital!” she implored, according to Andrés Bergen, the child’s father. Back when the elderly woman was young, her sister had died of measles. She had never forgotten the symptoms.

Artemio spent a week in the hospital, his parents hovering over him. His fever raged, and he struggled to breathe. “At a few points, we thought maybe he wouldn’t survive,” his father recalled. There is no antiviral treatment or cure for measles, and doctors generally treat the symptoms or manage complications. Finally, the boy recovered. On February 20, 2025, his parents brought him home, relieved the ordeal was over.

Then their other three children got sick.

‘Some kind of outbreak’

Measles can lead to serious complications and even death by triggering pneumonia or brain swelling. Bergen quickly realized that the illness was like nothing his kids had had before. One son was so pained by sunlight that his father covered the windows in black plastic. Another went limp. “He couldn’t even drink water at night by himself,” Bergen recalled.

The Esperanza (“Hope”) Mennonite school, which Artemio attended, has 240 students from kindergarten through high school. It’s a cheerful place, with colorful signs lining its whitewashed halls. “Be the ‘I’ in KIND,” reads one.

While Peters’ doctor had minimized the possibility of measles, the principal was concerned. He sent a note to parents warning of “some kind of outbreak.” Soon, one-third of the student body was out sick. Peters suspended classes, but the virus had already moved beyond his schoolyard.

“It was a matter of, I think, three or four weeks, and all the schools around had measles,” he recalled. They shut down, too.

In late March, Iris Ramírez, a state epidemiological official in the capital city of Chihuahua, 65 miles to the east, noticed something strange. Store clerks were coming down with measles. She said she soon made the connection: Mennonites from Cuauhtemoc traveled to Chihuahua on weekends to shop at Costco, Sam’s Club and other megastores. The virus came with them.

Measles quickly started circulating beyond Mennonites. Their farmhands played a key role in its spread, said Nakamura, the federal health official. Many were Indigenous seasonal laborers who came from poor, remote mountain villages with low vaccination rates.

The first to die in Cuauhtemoc’s measles outbreak was a 46-year-old Indigenous farmworker who was living not far from the Bergens’ house, regional health officials say. In early June, a 4-year-old girl died, the daughter of an Indigenous laborer in another Mennonite neighborhood. In addition to their lack of vaccines, some of the Indigenous suffered from malnutrition and other complicating factors for measles, the health officials said.

By the end of the year, the epidemic in Chihuahua state finally ebbed. But it had killed 21 people, 17 of them Indigenous.

And the virus was taking off elsewhere in Mexico.

Seminole, no exception to anti-vax information

Measles is so virulent that at least 95% of a community needs to be vaccinated with two doses of the measles, mumps and rubella (MMR) vaccine to avoid its spread, according to the World Health Organization.

Anti-vaccine information had spread in recent years to many parts of Texas. Seminole, a mostly Mennonite town of 7,000 in Gaines County, was no exception.

About 77% of kindergarteners in the county were reported to have received the measles shot for the 2024-25 school year, according to state records.

The Mennonite faith doesn’t prohibit vaccines. But the communities are often reclusive, with residents speaking Low German and keeping their distance from authorities.

The 9-year-old boy’s mother didn’t hear anything about measles during their family visit to Texas in January 2025, she said, and their relatives showed no sign of illness.

“I don’t know if we got it from Walmart” during a shopping outing, the mother said.

But after the family left Seminole, the virus exploded. In the following months, more than 760 people in the Texas town were infected, and 99 were hospitalized, according to the state health department. Two girls died. (An unvaccinated New Mexico man who also died tested positive for measles, in a related outbreak.)

Mennonites may be insular, but they’re also globalized. Families in the U.S. communities maintain close contact with relatives in Mexico and Canada. Anti-vaccine claims travel the same highways.

Dr. Alexis Hernández, the top state health official in Cuauhtemoc, recalled his employees’ surprise when they started knocking on Mennonites’ doors, urging them to get vaccinated. Some refused, holding up printed reports.

“They had scientific articles explaining why the vaccine shouldn’t be applied,” he said. “In English.”

In Mexico, money didn’t flow to vaccines

In Mexico, however, the problem wasn’t so much ideology as execution.

Its government follows more conventional public-health policies than the Trump administration, which named a vaccine skeptic – Robert F. Kennedy Jr. – secretary of Health and Human Services. Kennedy has issued mixed messages about measles shots, at times recommending them, but on other occasions saying they cause serious “adverse events,” and promoting unproven treatments. (The World Health Organization say the vaccine is safe and effective).

Mexico had established a top-notch vaccine program after a measles pandemic in 1989-90 left more than 8,000 dead. By the late 1990s, measles had been declared eliminated.

In recent years, however, the vaccine program withered amid cuts in health spending, the Covid pandemic and a botched restructuring of the national medical system.

“The government shifted its attention to other things,” said Alejandro Macias, an infectious disease doctor who helped lead the government response to the H1N1 flu pandemic in 2009. “The truth is, money didn’t flow to vaccines.”

In the Chihuahua region, only around two-thirds of 1-year-olds had received their recommended first measles shot in 2024, according to official data. A top state health official, Dr. Hugo Covián, told CNN that the federal government didn’t provide enough vaccines. “If we don’t have these drugs, of course we can’t reach adequate coverage levels,” he said in an interview.

Eduardo Clarke, a top federal Health Ministry official, denied that the vaccine budget had shrunk recently. The problem of declining coverage wasn’t a new one, he said, pointing to a study in the science journal Vaccines that found a 25% deficit in Mexico’s administration of measles vaccines between 2006 and 2024.

He dismissed allegations that vaccinations had plummeted under Sheinbaum’s mentor, former President Andrés Manuel López Obrador, whose term ended in 2024, saying that “if true, we would have had millions of cases.”

Still, over the years, the vaccination rate had fallen well below the US level, dipping below 80% by 2023, according to the study in Vaccines.

The ‘cruel math’ of virus growth

The real culprit in Mexico’s outbreak isn’t the 9-year-old who traveled to Texas, epidemiologists say. With measles still endemic in many parts of Africa, Asia and the Middle East, and flaring in towns in Canada and the United States, it’s inevitable a traveler will occasionally bring a case home.

That’s not a big deal in itself, says Dr. Carlos del Rio, a Mexican-born epidemiologist at Emory University in Atlanta.

“If vaccination rates are 96%, there’s no spread,” he said. But even a 90% coverage rate leaves a community exposed to the cruel math of exponential virus growth.

Officials note that there was limited impact when an unvaccinated 5-year-old girl arrived in the southern state of Oaxaca in January 2025, carrying a strain of measles common in Asia, where she had traveled.

“Fortunately, she ended up in a highly vaccinated community, and the virus only reached a small number of people,” said Nakamura.

In Cuauhtemoc’s Mennonite neighborhoods, local health officials say, only around 30% were vaccinated when measles arrived. It was like dropping a smoldering cigarette onto a pile of dry leaves.

Bergen, who runs an agricultural machinery company, recalls getting the measles shots as a child in school. But he decided not to vaccinate Artemio after the boy’s older brother had a bad reaction to lactose in another childhood vaccine.

The decision didn’t seem risky at the time, he recalled. “Measles was something our grandparents talked about,” he said. It belonged to another era.

Like other Mexicans, Bergen had also become more distrustful of the medical establishment during the Covid-19 pandemic. “We saw people who got the vaccine in worse shape than people who didn’t.”

About a half-dozen children at the Esperanza school ended up in the hospital with measles complications, especially breathing problems.

Many parents didn’t initially realize the potential severity of the illness, Peters said. Some suggested to him that all the children should become infected, to achieve natural “herd immunity” – an idea rejected as dangerous by most doctors. The parents in favor of vaccines began to fight with those opposed.

“I actually scheduled appointments with doctors for the parents,” the principal recalled. “I do not want children to pass away just because we’re being careless.”

Mexico’s response curbs cases

After the epidemic took off in Cuauhtemoc, health authorities scrambled. Many had never dealt with a measles case.

Hernández met with Mennonite leaders, who pledged their cooperation. Information about measles was translated into Low German. Teams of vaccinators scoured the Mennonites’ neighborhoods, offering shots to them and their agricultural workers. Soon the campaign swelled statewide. The teams provided shots to almost half of Chihuahua state’s roughly 4 million residents, said Clarke.

By early this year, though, the epicenter had shifted 800 miles south to Jalisco, a state with thriving agricultural and high-tech industries. State authorities were so alarmed they ordered students and teachers in Guadalajara, the capital, to wear face masks for several weeks, according to an official news release.

With a significant government vaccine campaign, the number of cases has since sharply declined, and just in time: Guadalajara is one of the host cities for the FIFA World Cup soccer tournament starting in June. In the past several weeks, Mexico has administered around 25 million shots nationwide, Clarke said.

In the United States too, weekly tallies of measles cases have dropped recently after outbreaks in Utah, Arizona, South Carolina and Florida, according to federal health data.

But Dr. William Moss, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health, said it was too soon to say the U.S. measles threat was over.

“It will all depend upon whether an infectious individual travels or ends up in a community of susceptibles,” he said. There are a growing number of such communities across the United States where people have opted out of vaccines.

And the toll of the outbreaks may yet increase. The measles virus can result in long-term damage, including a weakening of children’s immune systems. In rare cases, it can provoke brain or nervous-system damage long after the initial infection.

Bergen’s children appear to have bounced back from their illness.

“Up until now, we’ve seen no follow-up complications,” their father said.

For the next few years, though, he’ll be watching.

The-CNN-Wire
™ & © 2026 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved.