US and Mexico Face Loss of Measles Elimination Status as Outbreaks Mount

This week, behind closed doors, an advisory commission of the Pan American Health Organization is going through genetic data on measles. What it finds will help settle whether the United States and Mexico have lost the status of countries that have eliminated the disease. The U.S. had held that status for decades, and the evidence under review covers the outbreaks that have swept North America since 2024.

The question the commission is asking is narrow. Has the same measles virus been spreading continuously for a year or more? Dr. Amesh Adalja, an infectious disease physician in the Pittsburgh area and a senior scholar at the Johns Hopkins Center for Health Security, put it simply: the decision rests solely on genetics. If the answer is yes, the commission will say the countries can no longer be considered measles-free, because the virus is circulating within their borders. Last year PAHO took that step with Canada, which had held the designation since 1998. The commission's finding goes 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.

The U.S. earned elimination status in 2000, after vaccination campaigns pushed childhood measles vaccination above 97%. Experts say coverage of 95% is needed so that when an infected traveler arrives, enough people are protected that no outbreak starts. Rates have been slipping for years, partly because of disproven claims that the vaccine causes autism. Last year the national childhood rate fell to about 92%, and it was much lower in certain states and communities. Earlier this year President Donald Trump claimed, without evidence, that the MMR vaccine is possibly "quite lethal."

The numbers reflect that slide. 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 deaths have been recorded in the U.S. this year, more than in any year in over three decades, and 2026 is the worst year for measles illness since 1991. Measles typically begins with high fever and a rash that starts 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 blindness and brain swelling are more common in young children and in adults over 30.

Mexico's toll is heavier. Its vaccine arrived years after the first measles vaccine was licensed in the U.S. in 1963, 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 from that state 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 measles-related deaths, most of them children under 5.

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.

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 want more: a stepped-up, full-throated push for vaccination 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., a leading anti-vaccine voice before Trump put him in charge of the nation's health agencies. Kennedy has moved to shrink 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 vaccine. Experts say that runs counter to medical groups' recommendations and would likely leave fewer children fully vaccinated.

Dr. David Margolius, director of Cleveland's health department and a leader in a coalition of big-city health departments, called the expected decision "a big deal" and said it represents moving backward. The announcement next week should make it official.