MOHAVE COUNTY, Ariz. — The nation's second-largest measles outbreak this year is spreading beyond its epicenter along the Utah-Arizona border.
Most of the known measles cases — 123 as of Wednesday — are linked to a tight-knit community of twin towns: Colorado City, in Mohave County, Arizona, and Hildale, which is in Washington County, Utah. Within the past few weeks, there have been three cases in nearby, larger towns, such as Hurricane and St. George, Utah. Those exposures occurred in hospital and urgent care settings, according to the Southwest Utah Public Health Department.
There is no discernible border; residents live, work and worship interchangeably between the two towns.
Many of the clusters started in schools, said David Heaton, public information officer for the health department. "But now we have community spread," he said.
Measles has also reached Iron County, just north of the current outbreak.
The new areas are popular tourist destinations in southwest Utah, which is also home to Zion National Park.
All three affected counties have vaccination rates far lower than the 95% experts say is needed for herd immunity.
According to an NBC News data investigation, the vaccination rate in Iron County is 82.4%. In Washington County, it’s 79.2%.
It’s even lower in Mohave County, Arizona, at 78.4%.
Given the low vaccination rates, Heaton and his team had been bracing for a measles outbreak to hit the region. “We were preparing for it,” he said. “It was a matter of time before it came here.”
Most cases so far, Heaton said, are among unvaccinated school-age children. Five of Utah's six measles-related hospitalizations are in the outbreak center.
Across the United States, 77% of counties and jurisdictions have reported notable declines in childhood vaccination rates, according to NBC News data.
And the percentage of kids who didn’t get their recommended childhood vaccinations rose again last school year, continuing the post-pandemic trend of people opting out of vaccinations.
During the 2024-25 school year, 4.1% of kindergartners — about 138,000 kids — had vaccination exemptions, surpassing the previous record high of 3.7% during the prior school year.
Nearly all exemptions are listed as nonmedical, meaning the kids aren’t getting vaccinations for religious or other personal reasons.
Despite the government shutdown, the Centers for Disease Control and Prevention continues to tally national measles cases.
As of Wednesday, it reported 1,618 cases spread across 42 states, up from 1,596 last week. It's the most measles cases in the United States in 33 years.
