Key Takeaways:
- An unvaccinated Pennsylvania teen died from a rare neurological measles complication.
- The death marks Pennsylvania’s fourth measles-associated fatality in 2026.
- The Pennsylvania Measles Outbreak has reached nearly 700 cases across 38 counties.
An unvaccinated 18-year-old in Mifflin County, Pennsylvania, died from a rare measles complication Tuesday as the state reported its fourth measles-associated death of 2026.
Teen Dies From Rare Neurological Complication
The Mifflin County Coroner’s Office said the teenager died from acute disseminated encephalomyelitis, or ADEM, a rare and severe neurological complication of measles. Coroner Andrea L. Alcalde said an investigation and review of medical records established the cause of death.
“The cause of death was determined to be acute disseminated encephalomyelitis, a rare and severe neurological complication of measles,” Alcalde said in a statement. The manner of death was ruled natural.
ADEM can cause inflammation in the brain and spinal cord after an infection. Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia, said the condition can follow a measles infection when the immune system mounts a harmful response.
Pennsylvania Reports Four Measles-Associated Deaths
The Pennsylvania Department of Health said Tuesday that the teenager and a 40-year-old Jefferson County woman were both unvaccinated amid the Pennsylvania Measles Outbreak. The state had previously reported two measles-associated deaths involving infants in Lancaster County in August.
The department said its investigations with county coroners included clinical evidence of measles infection, a positive laboratory test and evidence that the deaths were not caused by unrelated conditions. The department uses the term “measles-associated” for deaths that meet those criteria.
The latest deaths are Pennsylvania’s first measles-associated fatalities in 35 years, state officials said. The United States recorded three measles deaths in 2025, while the four deaths reported in Pennsylvania this year represent the highest annual U.S. total since 1992.
Outbreak Spreads Across 38 Pennsylvania Counties
Pennsylvania has confirmed 693 measles cases across 38 counties this year, as the Pennsylvania Measles Outbreak continues to spread, according to the state. The outbreak is the state’s largest in more than three decades, officials said.
Nationwide, the Centers for Disease Control and Prevention had confirmed 3,294 measles cases as of Sept. 10. The CDC’s current national data page does not list any confirmed measles deaths for 2026 because the National Center for Health Statistics has no 2026 death records showing measles as the underlying cause.
Pennsylvania Secretary of Health Dr. Debra Bogen said officials are focused on containing the Pennsylvania Measles Outbreak and preventing additional deaths.
“My thoughts are with the two families who lost loved ones to this highly contagious virus,” Bogen said. She urged continued access to facts about measles and the measles, mumps, and rubella vaccine, which the state says provides 97% protection after two doses.
The CDC says measles remains highly contagious and can cause serious complications, including pneumonia and encephalitis. Two doses of the MMR vaccine provide about 97% protection against measles.
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