Public health, explained: Sign up to receive Healthbeat’s free national newsletter here.
Measles infections continue to spread across the United States, largely fueled by outbreaks – large and small – in multiple states
Since January, there have been more than 1,670 confirmed cases of measles nationwide, with most states reporting at least one case to the Centers for Disease Control and Prevention.
States with 10 or more confirmed cases of measles since January include: Arizona, California, Colorado, Florida, Minnesota, New Mexico, North Carolina, North Dakota, Ohio, Oregon, Pennsylvania, South Carolina, Texas, Utah, Virginia, and Washington state, according to federal, state, and local data.
But health officials in multiple states have told Healthbeat they are concerned measles cases are going unreported because there are people who aren’t seeking diagnosis and treatment. They also are worried that recent spring break travel may contribute to more people falling ill with measles in the next few weeks. It can take two to three weeks for symptoms to appear after a person is infected.
The good news: South Carolina, the site of the largest U.S. measles outbreak in decades with 997 cases, hasn’t had a reported measles infection in more than three weeks and will be declared over if that trend continues through April 26.
The bad news: Utah’s outbreak – now the largest, still-growing outbreak in the country – is approaching 600 known cases.
The CDC defines an outbreak as three or more related cases. Here’s what to know about six places where measles has been spreading:
Utah: The largest outbreak that is still growing
Utah’s large outbreak, like others, began with just a handful of cases that started being identified last June. A few were in Utah County, around Provo. Others were in a rural area in the southwest corner of the state – where the virus continued to gain traction, becoming the focus of the outbreak throughout last year.
By the end of 2025, 197 people had been diagnosed with measles largely in that one corner of the state. Then in recent months the outbreak surged statewide. Since January, another 386 people have been diagnosed, bringing the outbreak’s total to 583 reported cases as of this week. At least 47 people have been hospitalized.
Dr. Leisha Nolen, Utah’s state epidemiologist, said the number of cases known to public health officials is an undercount. “I can say confidently that we are missing cases,” she said.
But it’s difficult to say how many.
In some communities that are particularly distrustful of government and public health, as few as 1 in 10 cases may go unreported, she said. Cases in remote rural communities, with limited access to health care, may also have higher rates of underreporting, while more cases may get counted in cities with easier access to doctors and hospitals.
One thing is clear: Utah’s outbreak is continuing to grow. In the last three weeks, state health officials have learned of 121 new cases.
“In the beginning of our outbreak, we did have mostly communities along the southwest border with Arizona affected, and we were really trying to contain it in that area and prevent spread,” Nolen said. “But as you know, people move around.”
A state high school wrestling championship in mid February contributed to the spread of the disease, health officials said. The state’s TriCounty Health District in northeast Utah, with 59 reported cases, has been particularly hard hit in recent weeks following the event.
Kirk Benge, TriCounty Health director, said the region’s outbreak has been centered around the city of Vernal, which is known as “Dinosaurland” because of the area’s rich deposits of dinosaur fossils and nearby Dinosaur National Monument.
“We started with quite a large number of cases in a school,” Benge said. “Now we’re seeing the household spread that comes from all of those cases started in a school setting.”
There are encouraging signs the outbreak in the Vernal area may be slowing, he said.
“We saw week over week doubling there for a little while, and I think it plateaued here this last week, and it may be declining right now. So hopefully that trend continues,” Benge said.
He said that since the local outbreak began, large numbers of parents are seeking vaccines for their children and the number of vaccines administered is up 500% over the same period last year.
“I think we have a lot more just hesitant people who have been confused by mixed messages on social media,” Benge said. This kind of vaccine hesitancy is different than the staunch opposition to vaccination found in some other communities in the state, he said.
Still, many other parts of the TriCounty area remain vulnerable to measles outbreaks because of low vaccination rates – something the county’s board of health warned in a December 2024 open letter to the community that cited an increase from 4.8% to 11.9% of local parents seeking to exempt their children from school vaccines. “We want all residents to understand that individual decisions regarding vaccination impact us collectively,” the letter said.
To prevent outbreaks of measles, 95% of people in a community need to be vaccinated against the disease.
Arizona: Measles outbreak from 2025 continues to grow
A measles outbreak has been underway in Mohave County, along the Arizona-Utah border, since August 2025.
Last year the county had 214 cases. This year, at least 61 cases have been reported, state data show. Officials with the Mohave County Department of Public Health did not respond to an interview request.
Oregon: ‘Worrisome’ infections without obvious source
There have been just 13 measles cases reported across the state of Oregon as of April 3. While not technically an outbreak, Dr. Dean Sidelinger, the state’s epidemiologist, is concerned about hidden spread of the virus.
While the source of some of Oregon’s known measles cases can be traced to travel to another state with an outbreak, disease investigators haven’t found a source for most of the cases.
“That’s very worrisome to us in public health, because that indicates a level of spread in the community that we’re not detecting,” Sidelinger told Healthbeat.
The state’s wastewater testing has also been intermittently detecting measles in areas that don’t correlate with where cases are being reported, he said.
While Sidelinger said 9 out of 10 parents in Oregon have chosen to fully vaccinate their children, the state has localized communities where there are concentrations of unvaccinated people.
“Many of our communities, not just in Oregon, but across the country, who have lower vaccination rates, often have various reasons for that. But some are in more close knit, often faith-based communities that don’t typically seek health care, or maybe have a little bit more of a mistrust or distrust of government,” he said. “We worry that if it gets into one of these communities that it could spread fairly quickly.”
Florida: Cases continue in county with university outbreak
A measles outbreak linked to Ave Maria University in southwest Florida’s Collier County has grown to 106 confirmed and probable cases through April 4, the most recent data available on the state health department’s website. Statewide, there have been 144 measles cases reported since January, including a handful of cases in Broward, Pinellas and Hillsborough counties, the data show.
In recent weeks, spring break travel has resulted in a surge of travelers prompting concerns about the potential for further spread of the virus. The state health department and Ave Maria University didn’t respond to interview requests.
North Dakota: Two outbreaks since February
Since March 23 there have been six cases of measles reported in Ransom County, North Dakota, a largely agricultural area in the southeastern part of the state with a population of about 5,600 people. One person has been hospitalized, according to state data.
Officials at North Dakota Health and Human Services issued a press release on April 1 about the first Ransom County case, saying that the person “likely acquired the infection within the state” and that the case was not linked to a measles outbreak in Pembina County.
A spokesperson for the department said staff were out of the office and unavailable to answer questions about the current status of the outbreaks and efforts to control the spread of the disease.
The outbreak in Pembina County, which is in North Dakota’s northeast corner, involves 23 cases reported in February and March, according to the state’s online data. Four of these people were hospitalized.
A total of 32 cases have been reported across the state since January.
California: An outbreak sparked by travel to South Carolina
In recent months the Sacramento, California region has been experiencing a measles outbreak that was sparked by an unvaccinated toddler who had recently visited South Carolina’s outbreak area.
The toddler’s illness was reported to Sacramento County health officials in late February, then nearby Placer County identified three more measles cases in siblings from a different household who had been exposed to the toddler, according to the California Department of Public Health.
Additional cases have continued to be identified in both counties.
This week, Sacramento County announced that two additional measles cases have been reported. Both are unvaccinated children, raising the county’s number of confirmed cases to five.
“These five confirmed Sacramento County measles cases in recent weeks show the disease is circulating in Sacramento County,” the county health department said in an announcement about the cases. “The overall risk to the general public remains low but residents, especially those who aren’t vaccinated against measles or whose vaccination status is unknown, should be hyper-aware and take steps to protect themselves and others.”
In Placer County, where there have been eight confirmed measles cases, officials also are concerned that measles is spreading in the community. “Nearly all of the measles cases thus far have some association with homeschool enrichment programs in the region, either directly or through family members,” the county health department said.
Alison Young is Healthbeat’s senior national reporter. You can reach her at ayoung@healthbeat.org or through the messaging app Signal at alisonyoungreports.48.
