Wisconsin is reporting its first measles outbreak of the year, part of a nationwide resurgence of the disease taking hold across the country.
More than 4,800 cases – mostly children and teens – have been detected in 48 states since early 2025, when an outbreak began in a rural Texas community with relatively low vaccination rates against the disease, according to figures from the U.S. Centers for Disease Control and Prevention.
Since then, outbreaks have become recurring.
Measles, which is caused by a virus, is spread through the air and is highly contagious — much more so than even COVID-19 or chickenpox.
On Aug. 13, Wisconsin health officials announced a new outbreak, the second in as many years.
Here’s what we know.
Where is the latest measles outbreak in Wisconsin and how many cases have been identified?
The outbreak is concentrated in Iowa County in southwest Wisconsin. As of Aug. 13, a total of 15 confirmed and six probable cases had been linked to the outbreak. All but one were in Iowa County. The remaining case was in neighboring Lafayette County.
The latest cases bring the total number of measles infections reported in Wisconsin since January to 23. There were two cases earlier in the year, one in a University of Wisconsin-Madison student and the other in a Waukesha County resident. Both cases were related to international travel.
The latest cases were reported in August.
Is measles spreading in Iowa County or the area?
Wisconsin health officials suspect they have not identified every case of measles in Iowa County or the area and that the virus may be spreading.
“The rapid emergence of these cases, particularly among people who have not traveled outside of Wisconsin, indicates that there is active local transmission,” said Ryan Westergaard, chief medical officer and state epidemiologist for communicable diseases for the Department of Health Services.
“It’s very likely that additional cases exist in the community,” he said in an Aug. 13 call with reporters.
What is the vaccination status of the people who contracted measles in Wisconsin?
Most were not vaccinated against measles. Of the 23 measles cases reported since January, all but one were unvaccinated, according to the state health department.
What do we know about the people infected in Wisconsin’s latest measles outbreak?
Most of them are under 18 years old, and beyond that, we do not know much.
Of the 23 measles cases reported since January, three were under 5 years old, 11 were between 5 and 17 years old, and nine were adults, according to the state health department.
How did the latest outbreak in Wisconsin occur?
State health officials have not identified a source of the outbreak, Westergaard said Aug. 13.
The cases they have identified were transmitted in Wisconsin, meaning it is unclear who introduced the virus into the community and from where.
Where did they become infected?
State health officials have not released information about how the people infected were exposed or how they are connected to each other.
They have not given any more information about the location of the people infected beyond their county, citing privacy concerns.
Has anyone in Wisconsin been hospitalized with or died from measles?
None of the people infected with measles in the latest outbreak had been hospitalized as of Thursday, Aug. 13, Westergaard said.
The state Department of Health Services has reported one person hospitalized with measles so far this year. That may have been one of the two people who got sick back in January.
There have been no deaths.
Where might I have been exposed in Iowa County or the surrounding area?
State health officials have not notified the public of any locations that pose an exposure risk to the broader public.
Health officials say when they identify people who may have been exposed to the virus, they reach out to them individually.
“If an individual needs to stay home or there’s an exposure where people need to not gather, we’re doing that on an individual, case-by-case basis,” Westergaard said.
“If we can’t get a full accounting of who may have been exposed, that’s when we share information about public exposures,” he added.
If an exposure occurred at a day care, school or workplace, state health officials would not share that information with the public unless they were not able to identify everyone who may have been exposed and contact them, Westergaard said.
“The preference is always to respect people’s privacy and confidentiality and tell them one-on-one in a confidential setting this is where an exposure may have happened.”
What is being done to control the measles outbreak in Iowa County?
When public health officials identify a case, they investigate and conduct contact tracing to head off further spread.
In interviews with positive cases, public health workers try to identify others who may have been exposed and come into contact with an infectious person. They then reach out to those close contacts to ask about their vaccination status and to monitor for symptoms. Those exposed may be advised to quarantine.
“If we do all those things right, we can have a small outbreak that is contained and is over quickly,” Westergaard said. “That is our hope, and that is what we’re working really hard to do.”
What is the MMR vaccination rate in Iowa County?
Nearly 81% of 2-year-olds in Iowa County have had at least one dose of the measles, mumps and rubella vaccine, according to data from the state Department of Health Services. Among youth ages 6-18 years old, about 86% in Iowa County have received both doses of the vaccine, which is highly effective at preventing measles, according to DHS data.
Iowa County’s vaccination rate is higher than most other counties in Wisconsin for the MMR vaccine.
But it still lags behind the vaccination rate that public health experts recommend as a target for preventing outbreaks of measles. They aim for 95% vaccination rates in communities to keep measles from spreading.
“Virtually all of our counties are below 90% in terms of vaccine coverage,” Westergaard said. “When outbreaks or clusters occur, we need to work a little bit harder [to contain them].”
Neighboring Lafayette County has a much lower vaccination rate, with only 60% of 2-year-olds having received a dose of the MMR vaccine and about three-quarters of youth ages 6 to 18 years old up-to-date on the shot, according to state data.
Wisconsin health officials recommend that children receive the first dose of the MMR vaccine between the ages of 12 and 15 months, and a second dose between 4 and 6 years of age.
What are the symptoms of measles?
Measles symptoms typically start a week to two weeks after infection with a high fever, cough, runny nose and red, watery eyes.
A few days after the first symptoms arise, red spots or bumps appear on the face and near the hairline. That rash will spread to the rest of the body.
People may also get tiny white spots inside the mouth a few days after symptoms begin.
How can I protect myself against measles?
Public health officials say the best protection is the measles, mumps and rubella vaccine, which is long-lasting and highly effective at preventing illness. They recommend people check their vaccination status and get the shot if they are not up-to-date.
“This vaccine remains our single best tool to stop this and future outbreaks,” Westergaard said.
He also advised people to be aware of the symptoms of measles and to call their doctor or clinic before showing up if they come down with them.
Reporter Sarah Volpenhein can be reached at svolpenhei@usatodayco.com or 414-607-2159.
This article originally appeared on Milwaukee Journal Sentinel: Wisconsin measles outbreak may be spreading, no source found
Reporting by Sarah Volpenhein, Milwaukee Journal Sentinel / Milwaukee Journal Sentinel
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By Sarah Volpenhein, Milwaukee Journal Sentinel | USA TODAY Network
