During the same period, Mexico recorded over 17,000 cases. Measles is largely preventable with two doses of the widely available vaccine. However, the majority of those infected were unvaccinated.
Officials said the first case was detected in the neighborhood where the 9-year-old boy lived in Mennonite, an area established for growing apples, wheat, and corn in Chihuahua state, south of Texas.
The disease then spread to agricultural workers, many of whom belonged to indigenous communities.
By the end of 2025, the state had recorded approximately 4,500 cases, more than the total number of cases in the entire United States.
Precisely tracing the path of a microscopic pathogen is no easy task. However, Mexican officials believe the measles virus may have entered the throat or lungs of the unvaccinated third-grade student, and then spread rapidly.
From Canada to Mexico and then to Chihuahua
In Chihuahua, officials conducted genetic testing on more than 100 cases. All showed signs of the measles virus strain that first appeared in Canada in 2024 and then spread to Texas. Since then, the virus has spread to 32 states in Mexico.
"Everything originated from the outbreak in Chihuahua," said Dr. Miguel Nakamura, Director of Epidemiological Information at Mexico's Ministry of Health .
In the US, a series of measles outbreaks, starting with Seminole, have raised concerns about the spread of the disease.
Mexico's case is somewhat different. According to epidemiologists, what makes the outbreaks in these two neighboring countries similar is another factor: complacency.
Measles was declared eradicated in both countries more than a quarter of a century ago, considered a historic achievement in public health. However, according to epidemiologists, Mexico's once highly effective vaccination program has gradually weakened amid a chaotic state of the government-run healthcare system.
Thanks to the success of the vaccine, children no longer show signs of polio or complications of measles such as deafness or meningitis.
Spreads more rapidly than Covid-19.
Measles is one of the most contagious infectious diseases in the world, far more virulent than Covid-19. It spreads through coughing, sneezing, or even just talking. The virus can survive in the air for up to two hours. One infected person can infect up to 18 others.
Many cases present with mild symptoms. A 9-year-old boy returning from Seminole, Texas, developed a high fever and a rash but quickly recovered and returned to school.
Measles can lead to serious complications, even death, due to pneumonia or brain swelling.
According to the World Health Organization (WHO), at least 95% of the population in a community must receive both doses of the measles, mumps, and rubella (MMR) vaccine to prevent the spread of measles.
With measles still prevalent in many areas of Africa, Asia, and the Middle East, and outbreaks occurring in some towns in Canada and the United States, it is inevitable that people will occasionally bring the disease back from abroad.
According to Dr. Carlos del Rio, a Mexican-born epidemiologist at Emory University in Atlanta, if vaccination rates reach 96%, the virus will not be able to spread. But even at 90% coverage, communities still face the “cruel math” of exponential viral growth.
In the U.S., weekly measles cases have also decreased recently following outbreaks in Utah, Arizona, South Carolina, and Florida, according to federal health data.
However, Dr. William Moss, an epidemiologist at the Bloomberg School of Public Health at Johns Hopkins University, argues that it is too early to conclude that the threat of measles in the United States has ended.
“It will depend on whether a carrier travels to or appears in a community that is susceptible to infection. There are increasingly more such communities across the United States where people choose not to get vaccinated,” added Dr. William Moss.
The consequences of outbreaks may continue to escalate. The measles virus can cause long-term damage, including weakening children's immune systems. In rare cases, the disease can even cause brain or nervous system damage long after the initial infection.
Source: https://baovanhoa.vn/doi-song/dich-soi-bung-phat-lay-lan-manh-tu-my-sang-mexico-229044.html
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