In the three decades between 1993 and 2024, measles in the US was relatively rare—a few hundred cases each year, at most. But suddenly, the disease has become so entrenched in American life that it sometimes fails to make headlines when a new outbreak erupts.
As of March 2026, measles has been continuously circulating around the US for more than a year, starting with an outbreak in Texas that lasted from January to August 2025. Before that outbreak was declared over, an outbreak on the Utah and Arizona border began in August and is ongoing. An outbreak in South Carolina began in September, drastically increased in January 2026, and continues.
Thirty states have had measles cases this year; 47 have seen cases since the start of 2025. Health officials across the US have confirmed 1,300 infections already this year as of March 6, putting the country on track to surpass 2025’s numbers, which were the highest in 35 years.
We study outbreak preparedness and response at Brown University’s Pandemic Center, and we view the return of measles in the US as a grim signal of what’s to come.
Low levels of vaccination across the country mean measles outbreaks will continue to occur, needlessly hospitalizing and killing the unvaccinated. But beyond these harms, the disease’s resurgence serves as a serious warning about the country’s capacity to manage infectious disease threats of all kinds.
An eliminated disease returns
Measles’ return is no mystery: At its root is the falling vaccination rate.
Around 90 percent of the US population has received the MMR vaccine, which protects against measles, mumps, and rubella, and in some regions of the country, the rate is below 60 percent. Since about 2019-2020, that overall number has dropped below the 95 percent needed for herd immunity. It is necessary to keep that rate nationally, but maintaining herd immunity at the local level is equally important in order to prevent measles from finding pockets of unvaccinated communities.