After 26 years, the United States has lost its status as a country where measles transmission is considered eliminated. Widespread vaccination had kept the illness from continually spreading in the nation since 2000, but falling vaccination levels and surging case counts have erased that public health achievement.

An independent commission of experts reporting to the director of the Pan American Health Organization determined that the US no longer qualified for elimination status, a source close to the process told CNN on Friday. The Wall Street Journal first reported the decision.

The finding was widely expected, yet it remains a black mark on US public health policy. The international committee considers measles endemic, meaning regularly occurring, when infections caused by the same strain pass from person to person for at least one year within a country.

Committee members examine the genetic codes of viruses collected from patients to trace transmission. Viruses acquire tiny genetic changes as they copy themselves, allowing scientists to study how closely infections are related and whether they belong to the same transmission chains.

In August, scientists with Utah’s public health laboratory published a preprint study indicating that one measles strain had circulated in the state for more than a year. It accounted for more than 95% of cases there and caused more than 600 cases between June 2025 and June 2026.

The strain moved from southwestern Utah into the central part of the state. Sustained outbreaks have also occurred in South Carolina, Pennsylvania, Wisconsin, New York and other states.

It remains unclear which data the committee used in reaching its decision. Dr. Angela Rassmussen, a virologist at the University of Saskatchewan in Canada, said the Utah evidence alone would have been enough to establish the case.

The US has recorded unprecedented numbers of measles cases, hospitalizations and deaths during the past two years. This has happened as some members of the Trump administration, including President Donald Trump, have questioned the safety and effectiveness of vaccines that prevent the disease.

“Measles elimination is a vital sign for our public health system. It shows cracks in our foundation. Losing elimination status means that we are less prepared as a nation to address infectious and noninfectious disease challenges,” said Dr. Demetre Daskalakis, former director of the National Center for Immunization and Respiratory Diseases at the US Centers for Disease Control and Prevention.

Two doses of the measles-mumps-rubella vaccine reduce an exposed person’s chance of becoming sick by 97% compared with someone who is unvaccinated. After elimination was declared in 2000, sick travelers still brought measles into the country, but high vaccination rates generally kept resulting outbreaks small and brief.

During 2025 and 2026, the virus encountered more unvaccinated families and communities that were vulnerable to infection. More than 5,400 US cases have been reported this year, the highest total since 1991, with most connected to 43 new outbreaks and more than 1,000 linked to outbreaks that began last year.

Nearly all cases reported this year involved people who had not received the MMR vaccine or whose vaccination status was unknown. About 1 in 9 reported patients have been hospitalized, according to the CDC, while state reports show that at least 10 people have died after contracting measles.

The loss also increases the danger for people too young to be vaccinated and those with weakened immune function because of organ transplants, cancer or other conditions. Dr. William Moss of the Johns Hopkins Bloomberg School of Public Health said most patients recover after fever, rash and several miserable days, but the infection is not benign.

Measles can erase immune memory, leaving a person vulnerable to secondary threats such as pneumonia or diarrhea. Pregnant women can transmit measles to babies in the womb, while rare neurologic complications can emerge years later, including progressive and fatal subacute sclerosing panencephalitis.

Dr. Peter Hotez, co-director of the Center for Vaccine Development at Texas Children’s Hospital in Houston, called the loss “incredibly embarrassing.” He said its more important message was stark: “Basically, measles is back.”

Measles is among the most contagious viruses known to science, with one infected person typically spreading it to 12 to 18 others. The airborne virus can remain in a room for hours after an infected person leaves.

The Americas lost its measles free designation last year when Canada’s elimination status ended following a prolonged outbreak across several provinces. Mexico, which has experienced several large outbreaks, is also at risk of losing its status.

Regaining elimination status will not be simple, Moss warned, citing diminished vaccine trust, increasing nonmedical school exemptions, falling measles, mumps and rubella vaccination among kindergarten students, and the undermining of vaccine policy. “So it’s not going to be a trivial task for the United States to regain its measles elimination status.”