Arizona is now fighting its worst measles outbreak in nearly a decade

The worst Arizona measles outbreak in almost a decade keeps getting worse, as cases multiply in a small town on the Utah border where very few children have been vaccinated against the disease.

Colorado City, a town of about 3,300 people not far from the Grand Canyon’s north rim, is the epicenter of Arizona’s worst measles outbreak since 2016. Cases there doubled in a week, Arizona Department of Health Services data show. The youngest infected person is a 2-year-old.

The outbreak has moved fast. In early August, Mohave County reported one positive measles case: an unvaccinated person with no significant travel history. Since that initial case, the number of positive cases in Colorado City has ballooned rapidly. Within a week, the number of positive cases in the county jumped to nine. The next week, the cases increased to 12.

As of Wednesday afternoon, that number was up to 24 positive measles cases in the county.

Measles is rare but highly contagious. The illness can lead to serious complications, such as pneumonia and encephalitis, that can kill people, especially babies and young children.

Colorado City presents a tough battleground to fight the disease. People there have a history of vaccine hesitancy due to the town’s connection to the offshoot Fundamentalist Church of Jesus of Latter-day Saints, or FLDS. The town and its northern neighboring town in Utah, named Hildale, used to be a stronghold for ex-FLDS leader Warren Jeffs. In 2011, Jeffs was sentenced to life in prison, plus 20 years, for sexually assaulting young teens he’d taken as wives.

Amid the current outbreak, Mohave County is successfully convincing people to get vaccinated. More than 500 doses of the MMR vaccine have been administered in the little town during the past four weeks, said Danielle Lagana, a Mohave County Public Health spokesperson.

But health officials have a long way to go. According to ADHS data, only 78% of kindergarteners in Mohave County are vaccinated against measles — much lower than the rate required to achieve herd immunity. In Colorado City’s schools, the vaccination rate is even worse. One school has a 40% vaccination rate. In another, only 7.7% of students have gotten the MMR vaccine. Absent herd immunity, people who are medically unable to get the vaccine or who, like the 2-year-old, are too young to get their second shot, are left vulnerable to infection.

In Colorado City, the oldest person who has tested positive is 45 years old, Lagana said. Most of the people who have tested positive are children. The Colorado City Unified Governing Board confirmed at least one positive case in the schools after an eighth-grader tested positive at the town’s El Capitan High School on Aug. 11. The student and their siblings were sent home. But the schools in the area remain open.

Arizona has seen only one measles outbreak larger than this one, per the health department’s infectious disease stats, which go back to 2006. In May 2016, measles broke out at the Immigration and Customs Enforcement detention center in Eloy. The facility, which at the time housed roughly 1,500 detainees and employed 500 staffers, racked up 31 positive cases, per the Centers for Disease Control and Prevention, as 22 detainees and nine staffers tested positive for measles.

Everyone who tested positive for measles at the ICE facility was an adult. The staff contained the outbreak by giving the measles-mumps-rubella vaccine to all but one of the detainees in three days, according to the CDC.

Before that outbreak, the state’s largest measles outbreak was in 2008. Seventeen people, mostly children, tested positive in Pima County, which declared a public health emergency and rushed to vaccinate as many people as possible.

Earlier this year, President Donald Trump installed Robert F. Kennedy Jr. as the Secretary of Health and Human Services. Kennedy has made a career advocating for the rights of diseases to infect unvaccinated Americans. Unsurprisingly, 2025 is shaping up to be a banner year for measles.

Nationwide, U.S. measles cases hit their highest level this year since the disease was declared eliminated in 2000 due to the MMR vaccine. More than 1,430 measles cases have been reported across the country so far this year. Most of those are in West Texas, according to the CDC, with more than 400 cases reported in Gaines County alone. Arizona has confirmed 28 cases so far, beginning with four in Navajo County in June.

The MMR vaccine is 97% effective after two doses. The shot is generally provided to children between the ages of 12 months and 4 years. If the vaccine is administered within 72 hours of a person’s initial exposure to measles, the recipient gains protection against the disease or may experience milder illness, according to the CDC.