Upcoming meeting could determine if US loses its measles elimination status

A meeting is set to take place this week that will determine whether the United States has lost its measles elimination status.

An independent group of experts in epidemiology, public health, virology, pediatrics, and immunization, appointed by the Pan American Health Organization (PAHO), will review evidence to determine whether the U.S. has seen a year of continuous transmission.

The threat of the U.S. losing its elimination status looms, especially after Canada lost its measles elimination status last year after struggling to contain a year-long measles outbreak.

"At best, losing the elimination status would be a call to arms," Dr. Paul Offit, director of the Vaccine Education Center and an attending physician in the division of infectious diseases at Children's Hospital of Philadelphia, told ABC News. "To lose that status [would be] a tremendous loss."

How the U.S. earned measles elimination status

In the decade before the measles vaccine became available, nearly all children contracted measles by age 15, according to the CDC.

The federal health agency estimates that 3 to 4 million people in the U.S. were sickened by measles every year, about 48,000 were hospitalized and about 400 to 500 people died. About 1,000 people suffered encephalitis or brain inflammation.

In 1963, the first measles vaccine became available, followed by an improved vaccine in 1968. CDC data show that cases fell from 385,165 confirmed cases in 1963 to 26,686 cases in 1973.

In 1971, the measles, mumps, rubella (MMR) combination vaccine became available and, in 1989, the Advisory Committee on Immunization Practices, the American Academy of Pediatrics and the American Academy of Family Physicians recommended that children receive a second MMR dose.

By 2000, annual recorded cases had fallen to just 85, and measles was declared eliminated in the United States, meaning it was without continuous spread for at least 12 months.

"We should be proud as a nation that we were able to eliminate the world's most contagious infectious disease," Offit said. "That was an enormous accomplishment."

Current state of measles in the U.S.

Cases of measles were first confirmed to be cropping up in a small town in western Texas in January 2025.

Soon, the virus had spread to neighboring counties in Texas. Other states began reporting their own measles outbreaks, including Utah, Arizona, South Carolina and Pennsylvania.

Over the past nearly two years, 11 measles deaths have been confirmed, largely among unvaccinated individuals or those who were too young to be vaccinated.

It's unclear if the cases in Texas that were confirmed in January 2025 are linked to those in other states; if so, it would mean the U.S. has seen a year of continuous transmission.

"If it turns out all of those epidemics are entirely separate, and you can't string them together, then you can't say you've had 12 months of continuous transmission and we maintain our measles elimination status," Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine and co-director of the Texas Children's Hospital Center for Vaccine Development, told ABC News.

However, data may show there is genetically identical measles in all states where large outbreaks have been recorded.

"They may look at whether or not the strains that are circulating in those different communities are the same strains [first seen in Texas] or whether they're different strains," Offit said.

Last year, 2,289 confirmed measles cases were reported for all of 2025, CDC data shows. Prior to this, measles cases had not surpassed 2,000 in the U.S. since 1992. This year, at least 5,182 measles cases have been confirmed, mostly in 45 states and Washington, D.C.

How loss of elimination status works

The loss of status is determined by PAHO, an agency of the United Nations that oversees international health in the Americas.

An independent body of experts established by the PAHO -- known as the Measles, Rubella, and Congenital Rubella Syndrome Elimination Regional Monitoring and Re-Verification Commission -- meets at least once a year to monitor and re-verify measles and rubella elimination among countries in the region.

This year, the closed-door meeting will take place between Nov. 10 and Nov. 13.

A person familiar with how PAHO determines loss of elimination status told ABC News earlier this year that there would have to be compelling evidence that there has been continuous spread of measles in the U.S. since January 2025.

Offit and Hotez said the determination that the U.S. has lost its elimination status -- if it happens -- would merely be a formality.

"Measles is back," Hotez said. "Whether or not you connect the dots on these particular epidemics, to me, means less than the fact that we've just got so much widespread transmission in different parts of the U.S."