There have now been more measles cases in 2025 than in any other year since the contagious virus was declared eliminated in the United States in 2000, according to new data released Wednesday by the Centers for Disease Control and Prevention.

The grim milestone represents an alarming setback for the country’s public health and heightens concerns that if childhood vaccination rates do not improve, deadly outbreaks of measles — once considered a disease of the past — will become the new normal.

Experts fear that with no clear end to the spread in sight, the country is barreling toward another turning point: losing elimination status, a designation given to countries that have not had continuous spread of measles for more than a year.

“It’s a huge red flag for the direction in which we’re going,” said Dr. William Moss, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health who has studied measles for more than 25 years.

Most of the cases this year have been tied to the Southwest outbreak — the largest single outbreak since 2000 — which began in January in a Mennonite community in West Texas and has since jumped to New Mexico and Oklahoma.

But cases have also popped up in 38 states, which experts say represents a concerning vulnerability to diseases of the past. Because of the contagiousness of the virus, researchers often think of measles as the proverbial canary in a coal mine. It is often the first sign that other vaccine-preventable diseases, like pertussis and Hib meningitis, might soon become more common.