Measles spreading beyond the center of the Utah-Arizona outbreak
MOHAVE COUNTY, Ariz. — The nation’s second-largest measles outbreak this year is spreading beyond its epicenter along the Utah-Arizona border.
Most known measles cases — 123 as of Wednesday — are linked to a close-knit community of Twin Cities: Colorado City, in Mohave County, Arizona, and Hildale, in Washington County, Utah. In recent weeks, there have been three cases in larger neighboring cities, such as Hurricane and St. George, Utah. These exposures occurred at hospitals and urgent care settings, according to the Southwest Utah Department of Public Health.
There is no discernible boundary; residents live, work, and worship interchangeably between the two cities.
Many clusters started in schools, said David Heaton, public information officer at the Department of Health. “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.
The three affected counties have vaccination rates well below the 95% needed, experts say, for herd immunity.
According to an investigation of NBC News data, the vaccination rate in Iron County is 82.4%. In Washington County, it’s 79.2 percent.
It’s even lower in Mohave County, Arizona, at 78.4 percent.
Given the low vaccination rates, Heaton and his team were preparing for a measles outbreak to hit the region. “We were preparing for it,” he said. “It was a matter of time before he got here.”
Most cases so far, Heaton said, involve unvaccinated school-age children. Five of Utah’s six measles-related hospitalizations are at the center of the outbreak.
In the United States, 77% of counties and jurisdictions reported a notable decline in childhood vaccination rates, according to NBC News data.
And the percentage of children who did not receive recommended childhood vaccines increased again last school year, continuing the post-pandemic trend of people forgoing vaccinations.
In the 2024-2025 school year, 4.1% of kindergartners — or about 138,000 children — had vaccination exemptions, surpassing the previous high of 3.7% in the previous school year.
Almost all exemptions are listed as non-medical, meaning children are not vaccinated for religious or personal reasons.
Despite the government shutdown, the Centers for Disease Control and Prevention continues to track measles cases nationally.
As of Wednesday, it reported 1,618 cases spread across 42 states, up from 1,596 last week. This is the highest number of measles cases in the United States in 33 years.
