The US faces a critical deadline in January 2026 to prove it has stopped measles transmission and could lose its elimination status if large outbreaks linked to ongoing cases (like those from the Texas outbreak) aren’t definitively stopped and a 12-month period of no local spread is achieved. Following a surge in 2025 cases, including linked outbreaks in Texas, Arizona, and South Carolina, health officials are concerned that declining vaccination rates and continued spread might lead to this loss, mirroring Canada’s recent loss of status, though countries can regain it.1
In 2000, the United States achieved a major milestone in public health: measles elimination. This wasn’t the eradication of the virus worldwide — that remains a global challenge — but it meant that within the US, measles was no longer spreading endemically. New cases did occur, but these were linked to international travel and were quickly contained without sustained domestic transmission.2 That declaration didn’t mean the virus had vanished from the Earth — far from it — but it signaled that continuous, endemic transmission of measles inside the US had been successfully disrupted. It reflected decades of work by medical laboratory scientists, clinicians, public health agencies, epidemiologists, and communities who embraced the life-saving power of vaccines.
For more than two decades, this status stood as evidence of one of the most successful public health campaigns in modern history. Widespread vaccination, effective surveillance, and rapid outbreak response kept the virus at bay. But in 2025, this achievement is under serious threat. The US is experiencing its largest measles outbreaks in decades—and for the first time since elimination—experts are warning that the country may soon lose its measles elimination status.3
Global and Regional Trends
Measles cases have risen dramatically across the Region of the Americas in 2025, driven by multiple large outbreaks and importations. As of mid-September 2025, over 11,300 confirmed cases and 23 deaths were reported across 10 countries, a roughly 31-fold increase versus the same period in 2024. Canada, Mexico, and the US accounted for the vast majority. Earlier in the year, PAHO reported sharp increases compared with 2024 figures, reflecting ongoing gaps in immunization coverage that are fueling transmission.2 WHO has documented rising measles burden worldwide partly due to historical declines in vaccination coverage; tens of millions of children missed routine doses in recent years. While 2023 data showed ~10.3 million global cases, the 2025 landscape remains driven by outbreaks in multiple regions.4
United States Trends
As of December 9, 2025, the US has reported 1,912 confirmed measles cases, the highest annual total in over 30 years. Cases have been confirmed in 43 jurisdictions nationwide, with 47 outbreaks documented in 2025. Outbreaks are linked to under vaccinated or unvaccinated communities, and many cases trace back to international importations followed by local transmission. There have been 3 confirmed deaths from measles in the US. in 2025. Unvaccinated individuals account for the overwhelming majority of cases, consistent with patterns earlier in 2025 when ~96% of patients were unvaccinated or had unknown vaccination status.5
What Does Measles Elimination Mean?
To understand what’s at stake, it’s critical to define “measles elimination.” In public health terminology:
- Elimination is distinct from eradication. Eradication means the disease is gone globally (smallpox is the only human disease ever eradicated).
- Elimination means no continuous transmission of the disease within a particular geographic area for 12 months or more in the presence of a robust surveillance system.
The U.S. eliminated measles in 2000 primarily due to high 2-dose vaccination coverage with the MMR vaccine (measles, mumps, rubella).6 The 12-month clock resets any time there is sustained transmission that cannot be quickly stopped. If measles keeps circulating — without interruption — for more than a year, elimination status can be lost.
How Elimination Is Verified
Elimination status is verified by both national authorities like the Centers for Disease Control and Prevention (CDC) and international bodies such as the Pan American Health Organization (PAHO) and World Health Organization (WHO). Countries submit data on cases, genetic strains, and measures taken to interrupt spread. If sustained transmission occurs, the status is reevaluated and can be withdrawn.
Regional verification works similarly. For example, the Region of the Americas had maintained measles elimination status for years, but in November 2025 that regional status was lost after endemic transmission reemerged, particularly in Canada.7
The 2025 Measles Surge in the US
This year, the country has seen an unprecedented surge in measles cases; the highest in more than three decades.3 Multiple outbreaks have been reported, including significant activity in South Carolina, Utah, Arizona, and Texas. Some outbreaks have led to quarantines, hospitalizations, and even deaths. These numbers far exceed typical measles activity in the US after elimination and are far above the benchmark of fewer than 20 cases per one million population used to define a large or disruptive outbreak.8
The United States typically records a few dozen to a few hundred measles cases each year. These numbers, while concerning, are manageable for a strong public health system.
But 2025 has been different.
This year, the country has documented the highest number of measles cases in over 30 years, with outbreaks reported in over 40 states. Some states have experienced major transmission events linked to schools, community gatherings, and regions with lower childhood vaccination rates. Many of these outbreaks are genetically connected, which means they are not isolated sparks — they are part of a larger wildfire.
This level of sustained, cross-state transmission is exactly the type of scenario that threatens elimination status.
For over two decades, every time measles entered the US, it hit a “firewall” of vaccinated communities and fizzled out. This year, in too many places, that firewall didn’t hold.
Major Outbreaks Driving Spread
A key feature of 2025 has been linked outbreaks — clusters of measles that are genetically related and have been circulating for many months. A major outbreak that began in West Texas in January 2025 spread to Oklahoma and New Mexico and eventually seeded outbreaks in other states.9 Health officials believe this same measles strain (often referred to as subtype 9171) has continued to circulate for more than 10 months without interruption. If this continuous transmission crosses the 12-month threshold — likely around January 2026 — the U.S. would automatically be at risk of losing its elimination status. Again, by definition, continuous circulation of a measles virus strain for a year qualifies as endemic transmission, which undermines elimination.10
Why Are Measles Cases Rising?
There is no single reason. Instead, we’re facing a perfect storm of factors — scientific, social, structural, and behavioral.
1. Declining Vaccination Rates
The measles virus is one of the most contagious pathogens known. It can linger in the air for up to two hours and infects around 9 out of 10 susceptible people who are exposed to it. To prevent sustained transmission, communities need roughly 95% immunity through two doses of the MMR vaccine.
In recent years, national vaccination rates have dipped. In some local communities, they’ve fallen far below 90%. When vaccination rates decline, measles doesn’t politely stay away. It rushes in to fill the gaps.
In a recent Contagion interview, Ruth Lynfield, MD, discusses an approach clinicians can take in counseling parents who may have concerns about the MMR vaccine as well as other strategies to increase immunization adherence.