US and Mexico Face Loss of Measles Elimination Status as PAHO Experts Convene

This week, a closed-door meeting of a Pan American Health Organization advisory commission is weighing whether the United States and Mexico have lost one of their signal public health achievements: the elimination of measles. Experts widely expect the answer to be yes.

The commission is examining genetic evidence to determine whether the same strain of measles virus has been spreading continuously for a year or more in the outbreaks that have moved through North America since 2024. Dr. Amesh Adalja, an infectious disease physician near Pittsburgh and a senior scholar at the Johns Hopkins Center for Health Security, put it simply: the call rests solely on genetics. If the commission finds continuous spread, it will conclude that the virus has re-established itself in each country. It will present that finding to PAHO Director Dr. Jarbas Barbosa, a former Brazilian health official, who makes the final determination. PAHO officials say an announcement is being scheduled for next week. Last year, PAHO took the same step with Canada, which had held measles-free status since 1998.

The stakes are considerable. Measles is among the most contagious diseases known, yet vaccination had stopped its spread in the U.S. for 30 years. The country earned elimination status in 2000, after vaccination campaigns pushed childhood coverage above 97%. Experts say about 95% coverage is needed so that an infected traveler arriving in a community meets so many immune people that no outbreak takes hold. Dr. David Margolius, director of Cleveland's health department and a leader in a coalition of big-city health departments, called a loss of status a big deal and said it represents moving backward.

Coverage has been slipping for years, in part because of disproven claims linking the vaccine to autism. Last year the national childhood rate fell to about 92%, and it was far lower in certain states and communities. Earlier this year, President Trump claimed, without evidence, that the MMR vaccine is possibly "quite lethal." Large outbreaks erupted last year in Texas, Arizona, Utah and South Carolina. This year's more than 5,400 confirmed cases are already double the 2025 total, driven largely by an outbreak in Pennsylvania that has dwarfed the earlier ones. It is the worst year for measles illness since 1991.

The human toll is heavy. The U.S. has recorded nine measles-associated deaths this year, including a child whose death Wisconsin health officials reported Friday. That is more than in any single year in over three decades. Before the past two years, deaths from the disease were virtually unheard of in the country. About a dozen people have died across the recent outbreaks. Measles typically begins with high fever and a rash starting on the face and neck. Most people recover, but the World Health Organization lists it among the leading causes of death in young children, and complications such as blindness and brain swelling are more common in young children and adults over 30.

Mexico's situation is graver by the numbers. Cases began surging early last year, and more than 20,500 have now been confirmed nationwide. Fifty people have died, most of them children under 5. Researchers believe the outbreak in the northern state of Chihuahua traced back to an unvaccinated Mennonite child who traveled to Gaines County, Texas, where an outbreak was under way, and returned infected. Mexico only achieved elimination status in 2016, years after the U.S. began vaccinating following the vaccine's 1963 licensing. The problem extends beyond North America: early this year the WHO confirmed that Armenia, Austria, Azerbaijan, Spain, the United Kingdom and Uzbekistan had lost their status.

CDC Director Erica Schwartz said this week that losing the designation will not change how federal officials handle outbreaks. In her statement, she said vaccination, not the designation, protects Americans, and that the agency knows where transmission is occurring and is working with state and local health departments to reach those communities. Many public health experts argue the moment calls for a far louder vaccination campaign and more guidance for doctors. They fault what they describe as a politically fraught, muted federal response and blame Health Secretary Robert F. Kennedy Jr., formerly a leading anti-vaccine voice. Kennedy has moved to downsize the childhood vaccine schedule, reshape a key vaccine advisory board, and praised Trump's executive order calling for spacing out the measles, mumps and rubella vaccine, a step experts say contradicts medical groups' recommendations and would likely leave fewer children fully vaccinated.

The announcement from PAHO is expected next week.