Pennsylvania health officials announced on Tuesday that a fourth person in the state had died from measles, making 2026 the deadliest year for measles in the United States in decades. The Mifflin County coroner’s office said an 18-year-old died from a rare neurological complication of measles. The person was not vaccinated, according to the state health department. A coroner from another Pennsylvania county announced this week that a 40-year-old unvaccinated woman had died from measles complications. On Tuesday, that coroner, Greg Furlong, said that testing had confirmed the woman had contracted measles. Last month, state health officials reported the deaths of two infants who had measles.

Pennsylvania is facing a rapidly expanding measles outbreak that has sickened nearly 700 people and hospitalized more than 130 people. But there are likely to be many more measles cases that have not been reported, said Dr. Amesh Adalja, an infectious disease physician and senior scholar at the Johns Hopkins Center for Health Security. There are roughly one to three deaths for every 1,000 cases of measles, according to the Centers for Disease Control and Prevention, suggesting that the true case count in Pennsylvania is higher.

Measles deaths have been very rare in the United States since the disease was declared eliminated from the country in 2000. But as measles has come roaring back, more deaths have occurred. In 2025, two children and an unvaccinated adult died of measles, the first such deaths in a decade. “We are in the midst of a massive measles epidemic in the United States,” said Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia.

The Pennsylvania deaths have been embroiled in political controversy, with Health Secretary Robert F. Kennedy, Jr. disputing whether measles directly caused some of them. Last month, Dr. Erica Schwartz, the new director of the C.D.C., directed agency staff to not include the first two deaths in the national tally, going against the agency’s typical practice of accepting data reported by states. The C.D.C. has not recorded any deaths from measles this year.