In 2025, it seems like measles is everywhere. With more than 5,200 cases, Canada — and with it the region of the Americas as a whole — recently lost its measles elimination status. In the U.S., our own case counts continue to rise. Beginning with a large outbreak centered in an undervaccinated Mennonite community in West Texas, U.S. cases are now at the highest annual total in more than 30 years. This puts the U.S. in danger of losing elimination status in the coming months.
In February, a 9-year-old girl from Chihuahua, Mexico, returned home after a trip to Gaines County, Texas. After her return, she was diagnosed with measles — the first case in what is now an outbreak stretching across Mexico with more than 5,000 cases, mainly among unvaccinated children.
What does losing one’s measles elimination status really mean?
All the above is clearly bad news, but what does disease elimination — and in this case, losing one’s measles elimination status — really mean? Well, it doesn’t mean eradication, as in when a particular infectious agent (think smallpox and rinderpest, the cause of cattle plague) is wiped off the planet and we can let our guard down and stop vaccinating.
Elimination is a less-stable state that involves driving an infection out of a particular region. For measles, elimination means stopping the chain of transmission for more than a year in an area with a robust system for detecting cases.
It doesn’t mean zero cases. It means that the vaccine infrastructure and public health systems work so well that if someone with measles gets off a plane in your country, they don’t start a chain of transmission that keeps on going.
Measles is our most contagious disease, moving through human populations with an efficiency that flu, Covid and polio can only dream of. For this reason, we need vaccination rates above 95% to contain its spread.
I wrote a book about how measles’ exceptional contagiousness and the availability of a highly effective vaccine make measles outbreaks a reliable early warning sign of weaknesses in our public health systems.
But in addition to acting as a bellwether, measles is important in its own right. Despite Health and Human Services Secretary Robert F. Kennedy minimizing the disease’s danger and the insane “measles is good for you” rhetoric from some others in the anti-vaccine crowd, measles kills unvaccinated children and adults — even in 2025. This year, the U.S. has had three measles deaths, two of which were in previously healthy unvaccinated children. Canada has had two deaths, both in newborns whose mothers acquired measles during pregnancy, and Mexico’s outbreak has claimed 23 lives so far.
People who don’t die of measles can still experience hospitalization, life-changing complications including blindness or deafness and immune amnesia, which can increase the risk of severe infections for years after measles. In September, a child in Los Angeles died from subacute sclerosing panencephalitis, a degenerative neurological disease that can kill years after a measles infection. All these complications can be almost entirely prevented by vaccination.
We have had a safe, effective measles vaccine for more than 60 years. It’s a tool that has been used to eliminate measles from whole countries. So why does it seem like we are losing ground? Because controlling the world’s most contagious disease requires some things that are in dangerously short supply these days: international cooperation, sustained effort and investment and belief in the value of public health.
Controlling the world’s most contagious disease requires some things that are in dangerously short supply these days.
But due in large part to a distrust in science and vaccines, rates of measles, mumps and rubella, or MMR, vaccination among U.S. kindergarteners have decreased since the Covid-19 pandemic and are now well below the 95% threshold for outbreak prevention. Similar post-pandemic changes have led to decreased MMR use in Canada.
In the U.S., the rates of vaccination may drop further still given the near-constant stream of misinformation about MMR from the president and Kennedy replacing the members of the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices with a less-qualified, more conspiracy-minded cohort. Although the national MMR rates are lower than they should be, more than 9 out of 10 of American parents still vaccinate their children. State, county and even school-district-level rates may be more important indicators of areas at risk. In the lead-up to the West Texas outbreak, the statewide MMR vaccination rate was 94%, but the Gaines County rate was 82%, and one local school district in the county had fewer than 50% of its kindergarteners vaccinated. In Chihuahua, the health secretary there has estimated that less than half the Mennonite population is vaccinated. Undervaccinated Mennonite communities in Canada have been hard-hit as well, contributing to high case counts in Alberta and Ontario as well as spread among provinces. Isolated groups with low MMR uptake act as kindling for outbreaks. When the first case happens, the local vaccination rate is the difference between measles never gaining a foothold and an outbreak of hundreds or thousands of cases among unvaccinated kids, each with the potential to infect many more. This was true among Mennonites in Gaines County and Chihuahua and Alberta just as it was in an undervaccinated Orthodox Jewish community in a New York City neighborhood in 2018-19 when hundreds of measles cases required a sustained public health response and millions of dollars to control. The difference between a country that can maintain measles elimination and one that can’t isn’t whether measles cases occur. Until we eradicate measles, travel-associated cases will continue to test the defenses of all countries. Ensuring that public health systems are equipped to recognize when local vaccination rates drop and ready to intervene when they do is the only way to keep measles at bay.
Dr. Adam Ratner is a pediatric infectious diseases physician based in New York City and the author of "Booster Shots: The Urgent Lessons of Measles and the Uncertain Future of Children's Health." 
