US and Mexico Poised to Lose Measles Elimination Status as Outbreaks Persist

This week, in a closed-door session, a commission of international health experts is going through genetic data on measles in North America. The question before them is whether the United States and Mexico have lost the status of countries that have eliminated the disease. The advisory commission belongs to the Pan American Health Organization, known as PAHO, and it is looking at whether the same strain of the virus has been spreading continuously for a year or more in the outbreaks that began in 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 decision rests solely on genetics.

If the commission finds that it has, it will say neither country can still be considered measles-free, which means the virus has returned to sustained circulation. It will hand that finding to PAHO Director Dr. Jarbas Barbosa, a former Brazilian health official, who makes the final call. PAHO officials say an announcement is being scheduled for next week. Canada has already been through this: last year PAHO took away the status it had held since 1998.

For the U.S., the stakes are measured against a long record. Vaccination had stopped the virus from spreading domestically for 30 years, and the country was declared to have eliminated measles in 2000, after vaccination campaigns pushed childhood coverage above 97%. Deaths became virtually unheard of. Health experts say about 95% coverage is needed so that an infected traveler arriving in a community meets so many immune people that no outbreak starts. Dr. David Margolius, director of Cleveland's health department and a leader in a coalition of big-city health departments, called the likely decision a big deal and said it represents moving backward.

The numbers explain why. U.S. vaccination rates have slipped for years, partly because of disproven claims linking the vaccine to autism. Last year the national childhood rate fell to about 92%, and it was much lower in certain states and communities. Large outbreaks hit Texas, Arizona, Utah and South Carolina last year. This year's more than 5,400 confirmed cases are already double the 2025 total, driven largely by a Pennsylvania outbreak that has dwarfed the earlier ones. Eight measles-associated deaths this year are the most in any year in more than three decades, and it is the worst year for measles illness since 1991. Over the past two years, the outbreaks have caused thousands of illnesses and about a dozen deaths.

Mexico's situation is graver by count. Its vaccine arrived years after the U.S. began giving shots following the 1963 licensure, and it did not reach elimination status until 2016. Cases began surging early last year. Researchers think the outbreak in the northern border state of Chihuahua began with an unvaccinated Mennonite child who traveled to Gaines County, Texas, where an outbreak was underway, and returned infected. As of this week Mexico has reported more than 20,500 confirmed cases and 50 deaths, most of them children younger than 5.

Measles typically starts with a high fever, followed by a rash that begins on the face and neck. Most people recover, but the World Health Organization lists it among the leading causes of death in young children. Blindness and brain swelling are among the serious complications, and they are more common in young children and in adults over 30.

The federal response is a point of dispute. CDC Director Erica Schwartz said losing the designation will not change how officials handle outbreaks. In her statement she said vaccination, not the designation, protects Americans, that officials know where transmission is occurring and are working with state and local health departments to reach those communities. Many public health experts want more: a stepped-up campaign for vaccination and more guidance for doctors. They describe the federal response as politically fraught and muted, and they blame Health Secretary Robert F. Kennedy Jr., a leading anti-vaccine voice before President Trump put him in charge of the nation's health agencies. Kennedy has moved to downsize the childhood vaccination schedule, reshape a key vaccine advisory board, and praise Trump's executive order calling for spacing out the measles, mumps and rubella shots. Experts say that runs counter to medical groups' recommendations and would likely leave fewer children fully vaccinated. Earlier this year Trump claimed, without evidence, that the MMR vaccine is possibly quite lethal.

The problem extends beyond North America. Early this year the World Health Organization confirmed that Armenia, Austria, Azerbaijan, Spain, the United Kingdom and Uzbekistan had lost their status. PAHO's announcement next week will show whether the U.S. and Mexico join that list.