An infant in Wisconsin has died in connection with the state’s large, ongoing measles outbreak, the Wisconsin health department said Thursday. The death is Wisconsin’s first measles related fatality in more than 35 years and the third reported in the United States this week.

The coroner listed measles as the immediate cause of the infant’s death, according to the health department. Officials said no additional details about the child would be released in order to protect the family’s privacy.

“My heart is broken for the family,” said Kirsten Johnson, secretary of the state’s health department.

“Any death of a child is a tragedy and even more so when it is related to a vaccine-preventable disease.” Johnson added, “Measles can cause serious illness and death, and it is important for all Wisconsinites to evaluate their risk and take steps to protect themselves and their family.”

Wisconsin is experiencing its largest measles outbreak in more than three decades. As of Thursday, the state had recorded 431 cases across 13 counties this year, a count that health officials cautioned almost certainly falls short of the actual total.

The health department said the real number is likely higher because some people who become sick do not seek medical care. That can leave cases outside the official count during an outbreak that has already spread across multiple counties.

Wisconsin reported 36 measles cases in 2025, providing a sharp comparison with the 431 cases recorded this year. In the past, most cases were associated with international travel, according to the state.

The current spread is also linked to domestic travel and exposure to relatives and other people in the community. That shift comes as health officials confront vaccination coverage that remains below the level needed to stop measles from moving through a population.

Nine people in Wisconsin have been hospitalized. Anyone with measles can develop life threatening complications, including pneumonia or swelling of the brain, but some groups face a greater risk of severe disease.

Those at higher risk include children younger than 5, people with weakened immune systems and people who are pregnant. Health officials are urging residents to assess their exposure risk while the outbreak continues.

The state is encouraging everyone who has not been vaccinated to receive a measles vaccine. Two doses of the measles, mumps and rubella vaccine are 97% effective at preventing measles, according to the health department.

MMR vaccination coverage among Wisconsin kindergarteners is about 85%. That is well below the roughly 95% coverage health officials say is necessary to prevent measles from spreading through a population.

“That’s really the central issue here: Measles is now spreading because there are enough people who are susceptible to infection for the virus to continue finding new hosts,” said Dr. Ryan Westergaard, Wisconsin’s chief medical officer and state epidemiologist for communicable diseases.

Wisconsin’s health department updated its guidance this week as the outbreak continued. It now recommends an early MMR dose for certain infants between 6 and 11 months of age who face an increased risk of exposure.

MMR vaccination typically does not begin until a child’s first birthday. The revised guidance creates an earlier option for certain infants considered more vulnerable to exposure during the outbreak.

Until 2025, the United States had gone years without a measles death. Three measles related deaths have now been reported this week, including the infant’s death in Wisconsin.

In Pennsylvania, an unvaccinated resident of rural Jefferson County died after testing positive for measles, the Pennsylvania Department of Health said Wednesday. The county is in the north central part of the state, and the person was Pennsylvania’s sixth measles death this year.

The New York State Department of Health announced Monday that a child had died after contracting measles. The child lived in rural Lewis County in northern New York, and the death was the state’s first from measles in 30 years.

More than 4,800 measles cases have been reported across the United States this year, according to the US Centers for Disease Control and Prevention. That is the highest annual total since 1991, almost a decade before measles was declared eliminated in the country.

An international meeting is scheduled for next week to determine the status of measles elimination in the United States. The review will come as the country confronts its highest case count in decades and multiple reported deaths.