Measles Returns: Why the U.S. Could Lose Elimination Status — and What That Would Mean

In 2025 measles has reappeared across large parts of North America. Canada has reported more than 5,200 cases, and the Region of the Americas recently lost its measles elimination designation. In the United States, case counts are rising after a major outbreak that began in an undervaccinated Mennonite community in West Texas; the current annual total is the highest in more than three decades, placing the U.S. at risk of forfeiting elimination status.

How one imported case can ignite an outbreak

In February a nine-year-old girl from Chihuahua, Mexico, returned home after visiting Gaines County, Texas, and was diagnosed with measles. That single importation is now linked to an expanding outbreak in Mexico with more than 5,000 cases, largely among unvaccinated children. These cross-border chains show how fragile regional control can be when pockets of low vaccination persist.

What “elimination” actually means

Elimination is not eradication. Eradication — like smallpox — means a pathogen is gone worldwide. Elimination is a regional achievement: it means stopping sustained chains of transmission for at least 12 months in an area that maintains reliable surveillance. It does not prevent imported cases; it means the public-health and immunization systems are strong enough that an importation will not spark ongoing, uncontrolled spread.

Why measles is so dangerous

Measles is the most transmissible human infectious disease — far more contagious than seasonal influenza, COVID-19 or polio. To prevent sustained spread we need population immunity generally above ~95 percent. Measles causes severe outcomes: this year the U.S. has recorded three confirmed measles deaths (including two previously healthy unvaccinated children), Canada has reported two deaths in newborns whose mothers contracted measles during pregnancy, and Mexico’s outbreak has claimed 23 lives to date. Survivors may still face hospitalizations and permanent complications such as blindness, deafness and immune amnesia, which raises the risk of serious infections for years after illness. In September a child in Los Angeles died from subacute sclerosing panencephalitis (SSPE), a progressive neurologic disease that can appear years after measles.

What’s driving the resurgence?

Several factors have combined to create the current risk: declining MMR (measles-mumps-rubella) coverage since the COVID-19 pandemic, clustered communities with low vaccine uptake, and the spread of misinformation that reduces trust in vaccines and public health. Nationally, more than nine in ten American parents still vaccinate their children, but local coverage varies widely — and outbreaks are driven by community-level gaps. For example, before the West Texas outbreak Texas’ statewide kindergarten MMR rate was about 94%, but Gaines County’s rate was roughly 82% and one local school district reported under 50% of kindergarteners vaccinated. Health authorities in Chihuahua estimate fewer than half of some local Mennonite populations are vaccinated. Similar pockets in Canada helped fuel outbreaks in Alberta and Ontario.

The role of policy and public trust

Public-health investment, robust surveillance, international cooperation and sustained vaccination efforts are essential to maintain elimination. Policy decisions, leadership messages and shifts in advisory committees can influence public confidence and program effectiveness. When trust and resources decline, measles — because of its high transmissibility — becomes a sensitive early-warning signal for broader weaknesses in health systems.

What can be done now

Maintaining elimination requires four core actions: (1) restoring and sustaining high MMR coverage, especially in localities with low uptake; (2) reinforcing case detection and outbreak response capacity; (3) countering misinformation with clear, evidence-based communication; and (4) investing in public-health infrastructure and international collaboration to prevent and quickly interrupt importations.

Bottom line: Until measles is eradicated globally, imported cases will occur. The difference between occasional, contained importations and large outbreaks is whether local vaccination coverage and public-health systems are prepared to detect and act. Vaccination remains the overwhelmingly safe and effective way to prevent the severe harms of measles.