Copyright The Boston Globe
“We certainly have not had anything like this in many, many, many years,” said Walter Ornstein, an emeritus professor at Emory University and former director of the United States Immunization Program at the Centers for Disease Control and Prevention. There are several parallels between the current situation at the Utah-Arizona border and the outbreak that exploded from the Western edge of Texas in January — both started in rural towns with a sizable population of children who had not been immunized against measles, mumps, and rubella. And in both outbreaks, the virus traveled to a neighboring state and took root in similarly vulnerable pockets. “I’m worried about it,” said Dr. Adam Ratner, a pediatric infectious disease expert who recently published a book about the resurgence of measles. “I think it’s a very similar situation.” But experts have also noticed a key difference. For the last two decades, most large measles outbreaks have had ties to close-knit communities that have long had low vaccine uptake, said Dr. William Moss, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health who has studied measles for more than 25 years. The 2019 measles outbreak in New York, for example, almost exclusively spread through communities of ultra-Orthodox Jews. The largest outbreak before that, in 2014, was overwhelmingly confined to an Amish community in Ohio. And the outbreak in West Texas earlier this year spread mainly through a large Mennonite community. In the current outbreak, cases have been clustered in Colorado City, Arizona, and Hildale, Utah — adjoining cities with historical ties to the Fundamentalist Church of Jesus Christ of Latter-day Saints, a polygamist offshoot of the Mormon church. However, local public health officials said the virus had spread beyond members of that religious group into the broader community, where vaccination rates have dropped steeply since the pandemic. In Mohave County, Arizona — which now has the second-highest case count of 2025, only after the Texas county at the center of the Southwest outbreak — roughly 90 percent of kindergartners were fully vaccinated against measles in the 2019-20 school year. But by the 2024-25 school year, the vaccination rate had dropped to 78 percent. About 95 percent of a community needs to be vaccinated to stem the spread of measles, which is one of the most contagious known viruses. Data from Southwest Utah tell a similar story: Vaccination rates dropped nearly eight percentage points over the course of the pandemic to about 78 percent. Moss said it comes as no surprise that this outbreak has taken root in states with relaxed laws surrounding school vaccine mandates. Both Utah and Arizona allow parents to opt their children out of those requirements for personal, religious, or medical reasons. In Mohave County, the percentage of kindergartners with personal exemptions nearly doubled from the 2019-20 school year to the 2024-25 school year. Exemption rates in Southwest Utah, the vast majority of which were attributed to personal beliefs, also nearly doubled during that time period. “We’ve just been holding our breath and waiting for this to happen,” said Jessica Payne, an epidemiologist who leads the immunization program at the Utah Department of Health and Human Services. “Now it has.” Measles symptoms typically resolve in a few weeks. But in severe cases, the virus can cause pneumonia, making it difficult for patients, especially children, to get oxygen into their lungs. It may also lead to brain swelling, which can cause lasting damage, including blindness, deafness, and intellectual disabilities. This year, one in every eight people diagnosed with measles was hospitalized, and two children died, the first such deaths in the country in a decade. In addition to helping coordinate the public health response in Utah and Arizona, the CDC is also lending experts to health departments in Minnesota and South Carolina, which have smaller measles outbreaks, said Andrew Nixon, a spokesperson for the Department of Health and Human Services. Local health officials are still investigating how exactly the outbreak at the Utah-Arizona border began. While they believe the first case was in a resident exposed to the virus while visiting another state, it’s not yet clear whether there is a link to cases from the Southwest outbreak.
