WASHINGTON- The United States has lost its measles-elimination status after 26 years, following the re-establishment of sustained transmission of the highly contagious disease, marking a major setback for the country’s public health system.
The decision was made by the Pan American Health Organization’s (PAHO) Regional Monitoring and Re-Verification Commission for Measles, Rubella and Congenital Rubella Syndrome, according to Reuters, after the same measles virus strain continued circulating in the United States for at least 12 months.
The US had maintained measles elimination status since 2000, when endemic transmission of the virus was declared eliminated.
Under PAHO’s criteria, endemic transmission is considered to have been re-established when epidemiological and laboratory evidence shows that the same viral strain has been transmitted continuously for 12 months or longer within a country or defined geographic area.
The loss of status comes amid a sharp resurgence of measles in the US.
The US Centers for Disease Control and Prevention reported 5,412 confirmed measles cases as of November 12, 2026, making this the country’s worst measles outbreak in decades and the highest annual total since 1991.
At least six measles-related deaths have been confirmed by the CDC in 2026, while state health authorities have reported additional deaths associated with the outbreaks. Pennsylvania and Wisconsin reported measles-associated deaths this week, while New York reported its first known measles-associated death in more than three decades earlier this month.
Falling vaccination coverage fuels resurgence
The resurgence has been driven largely by outbreaks in communities with low vaccination coverage.
Measles is among the most contagious infectious diseases. High vaccination coverage is therefore critical to maintaining population-level protection and preventing the virus from regaining a foothold.
Two doses of the measles, mumps and rubella (MMR) vaccine provide about 97% protection against measles.
For years, imported cases continued to occur in the United States, but high vaccination coverage generally prevented them from developing into sustained transmission.
That protection has weakened as vaccination rates have declined and vaccine hesitancy has increased in some communities.
The consequences have been significant. PAHO reported that the United States had recorded 4,410 confirmed measles cases by epidemiological week 41 of 2026, with the country among those contributing most to the sharp increase in measles cases across the Americas.
A setback for decades of progress
The loss of measles elimination status represents a significant reversal of public-health progress.
The Americas became the first region in the world to achieve measles elimination in 2016, following decades of vaccination and disease surveillance.
However, maintaining elimination requires countries to prevent sustained transmission after imported cases enter their populations.
PAHO says losing elimination status can increase the risk of outbreaks, place additional pressure on health systems and reverse gains made through immunisation programmes.
The United States is now the second major country in the Americas in recent years to lose its measles elimination status after Canada experienced sustained transmission.
US can regain elimination status
The loss of status is not permanent.
PAHO’s framework requires a country to interrupt endemic transmission for at least 12 consecutive months before elimination status can be restored. Countries must also strengthen vaccination, surveillance and outbreak-response systems and submit evidence demonstrating that sustained transmission has been interrupted.
Brazil provides an example of how elimination status can be regained. After losing its status in 2019, Brazil interrupted endemic transmission and was re-verified as measles-free in 2024.
For the United States, however, regaining that status could prove challenging amid declining vaccination coverage and growing vaccine hesitancy.
The development is a warning that measles elimination is not a permanent achievement but one that depends on maintaining high vaccination coverage, strong surveillance and rapid outbreak response.
Measles is highly preventable, but once vaccination coverage falls, the virus can rapidly exploit gaps in population immunity.
