A child gets an MMR vaccine at a clinic in Lubbock, Texas, in March 2025. Wisconsin experts say vaccination rates here are lower than they should be to guard against a wider outbreak. (Photo by Jan Sonnenmair/Getty Images)

With three measles cases in three different Wisconsin communities since New Year’s Day, the state could be vulnerable to a larger outbreak, according to public health experts.

“We’ve gotten three cases in the state of Wisconsin so far in 2026, and there’s been many years in which we had zero,” said Dr. Joe McBride, a pediatric infectious disease physician at UW Health Kids and assistant professor of medicine at the University of Wisconsin School of Medicine and Public Health. If the cases spread, “those are incredibly, incredibly difficult for us to slow down and to prevent.”

“There may be only three people with measles, but the cases are occurring in three different places,” said Ajay Sethi, director of the Master of Public Health Program at the UW medical school. “These are three separate public health responses, and that is significant given the potential for spread to others from just one person with measles.”

In January, state health officials reported a measles infection in a Waukesha resident. This month, measles infections have been identified in Dane County and in a person who traveled through Milwaukee County’s Mitchell International Airport to Walworth County. The Wisconsin Department of Health Services has also identified possible locations when other people might have been exposed in the Dane County and Mitchell Airport cases. All three were described as connected to travel. 

“It’s good, in that they don’t seem to be related, and we don’t see an outbreak,” McBride said. “But it’s also bad because that means there’s a lot of measles,” he added. “It’s kind of a tinderbox, and we have large cohorts of our population who are not immune.”

The year 2025 saw a resurgence of measles nationwide, approaching 2,000 cases, Stateline reported in December, with outbreaks in Texas, Arizona, South Carolina, Utah and New Mexico.

Sethi said an August 2025 cluster of cases in Oconto County started with a case in St. Croix County in someone who was visiting from out of state. Across Wisconsin in 2025, “Ultimately 36 people got measles, and two of them needed hospitalization,” he said.

‘Incredibly infectious’ illness

Although most widely known for its trademark rash, the measles virus “is a respiratory virus, just like really any other cough and cold virus that we think about,” said McBride. “However, it’s incredibly, incredibly infectious.”

The virus is airborne, McBride said, and can hang in the air for up to two hours. In one landmark case, at the 1991 Special Olympics at the Minneapolis Metrodome, a participant on the field had measles, McBride said, “and people who were susceptible to the infection got the infection who were sitting in the upper deck.”

Vaccination is the primary tool to stop measles, and in Wisconsin as well as in much of the U.S. vaccination rates are below the 95% that public health practitioners say allows for widespread “herd immunity.”

The measles vaccine is usually given in combination with mumps and rubella vaccines, first at the age of 1 with a booster by the time a child is 5.  

Some people aren’t eligible for the vaccine, either because they’re younger than 6 months old or because they have a compromised immune system due to another illness.

“It’s a live vaccine, and live vaccines have the potential of causing infections in people who are immune-compromised, like bone marrow transplant recipients or a patient with AIDS” or people on medications that suppress the immune system, McBride said.

That makes it even more important for people who are eligible to get the vaccine, public health experts say.

A national map produced by ABC News in collaboration with Boston Children’s Hospital, Harvard Medical School and Icahn School of Medicine at Mount Sinai in New York shows that none of the counties in Wisconsin has as many as 90% of  5-year-olds fully vaccinated for measles.

The lowest rates of measles vaccinations for that age group are in Portage and Columbia counties, with fewer than 60%. A cluster of counties around Oshkosh have vaccination rates in the low 60s; another cluster around Eau Claire in the mid-60s, and Milwaukee, Racine and Waukesha counties have vaccination rates in the high 60s. In the rest of the state, vaccination rates for children 5 or younger are in the range of 70% to more than 80%.

“The decision to get vaccinated is still very nuanced,” Sethi said — influenced by a variety of factors. Those include complacency, which may lead people to dismiss the need for a vaccine, he said. Other factors include how convenient it may be to get the shot, confidence in the vaccine’s effectiveness and a sense of community responsibility.

HHS shift, CDC silence

One source of shakier confidence has been a shift at the U.S. Department of Health and Human Services and the Center for Disease Control and Prevention (CDC), in the agencies’ stance on vaccines under HHS Secretary Robert F. Kennedy Jr., who had a history of anti-vaccine campaigning for years before his appointment.

Kennedy has made some appeals for people to get the measles vaccine, and in an appearance on CNN Sunday, Dr. Mehmet Oz, director of the Centers for Medicare & Medicaid Services, urged viewers, “Take the vaccine, please.”

But researchers at Johns Hopkins University in a report published in December documented that amid the 2025 measles surge, CDC social media accounts “have gone quiet, creating a ‘void’ in online health communication. In this vacuum, measles messaging has been dominated by news media rather than expert health authorities, resulting in polarized and potentially inaccurate information.” 

By the year 2000, measles vaccination had become so widespread that the U.S. was identified as having eliminated the disease. Canada, which also had that status, lost it in 2025, and the U.S. appears to be on the verge of losing it as well, Sethi said.

Yet the measles vaccine is both extraordinarily effective and essentially the only weapon against the virus.

“There isn’t any kind of other medicine that can abort it,” McBride said. “It is completely dependent on either preventing it or having natural infection and supporting the individual through it.”

The infection itself can be extremely serious, however, he said. In addition to fevers, cough and the rash, which is painful, secondary complications can do much more bodily damage. Those can include bacterial infections, pneumonia, vision and neurological damage and cardiovascular system harm as well.

In about one of every 1,000 cases, a delayed neurological condition can arise 10 years after a person is infected “that is completely fatal,” McBride added. Among the hundreds of cases across the U.S. now, “there certainly is somebody who’s walking around today who will be dead of measles in 10 years, who doesn’t know it. And that’s incredibly scary.”

People born before 1957 are more likely to have natural immunity from having been exposed to measles in childhood. “After 1957 we can’t really make that claim for people,” McBride said. “And so our immunity is dependent on vaccine status.”

People living in Wisconsin can look up their immunization status on the Wisconsin Immunization Registry, McBride said. Some people’s records might be incomplete, either because they received a vaccine in another state or because they got a vaccine before 1999, when the registry was launched. Earlier vaccines were logged on paper by health providers, according to the Wisconsin Department of Health Services.

Interest in the MMR vaccine appears to be rising. News reports and public health announcements drawing attention to recent measles cases and the importance of the vaccine “certainly raises new awareness and attention to it,” he said.

More patients are asking about the shot and more doctors and nurses are asking whether there needs to be any changes to the current vaccine schedules recommended by the American Academy of Pediatrics or the state health department.

McBride said the current cases in Wisconsin don’t point to any change in those recommendations, however. For health care providers, “The most helpful interventions would be to evaluate your patients and make sure they are up to date with the measles vaccine.”