Eight measles-related deaths have been reported across the US this year after an infant died in Wisconsin, marking the country’s deadliest outbreak of the disease in decades, according to state health department figures.
The Wisconsin Department of Health Services announced the death on Thursday, the state’s first measles-related fatality since 1990, as an outbreak continues in its southwestern counties.
Pennsylvania has recorded six deaths, while New York has reported one, with three of the fatalities announced this week.
The Centers for Disease Control and Prevention (CDC), however, has officially recorded only four measles-related deaths this year, reflecting a discrepancy between federal and state reporting figures.
According to the CDC’s latest figures, 5,182 infections had been confirmed nationwide as of this Thursday, more than double the 2,289 recorded throughout 2025.
Wisconsin alone had reported 431 cases across 13 counties as of November 3, its highest total in more than 35 years.
Pennsylvania has been particularly hard hit, with nearly 1,500 cases reported since an outbreak began in April.
Health authorities have urged residents to check their vaccination status and receive the measles, mumps and rubella (MMR) vaccine if necessary.
The resurgence has raised questions about whether the US could lose its measles elimination status, granted in 2000 after sustained domestic transmission of the virus was halted. The Pan American Health Organization is expected to review the country’s status next week.
Health authorities have linked the spread of the highly contagious disease to declining vaccination rates. CDC data show that coverage among kindergarteners has fallen from 95.2% in the 2019-2020 school year to 92.4% in 2025-2026.
In August, President Donald Trump signed an executive order calling for separating the combined MMR vaccine into individual shots, drawing criticism from medical groups warning that the move could discourage vaccination.
The CDC recommends two doses of the combined MMR vaccine, which it says provides approximately 97% protection against measles.
The disease typically causes fever, coughing, a runny nose and a rash, but can also lead to life-threatening complications, including pneumonia and brain swelling. Children under five, pregnant women and people with weakened immune systems face particularly high risks.
Before widespread vaccination began in the 1960s, measles claimed up to 500 lives annually in the US, according to CDC estimates.