Pennsylvania health officials have reported a fourth death linked to measles, marking the worst year for the disease in the state since 1991. The latest fatality involved an 18-year-old from Mifflin County, whose cause of death was listed as acute disseminated encephalomyelitis (ADEM), a rare but severe neurological condition that can develop as a complication of measles. This brings the total number of measles-associated deaths in Pennsylvania to four, with all four occurring in the last month. These are the first such deaths in the state in 35 years. The two most recent deaths were a 40-year-old woman from Jefferson County, who passed away on Saturday due to complications from measles, and the Mifflin County resident. Before that, two infants in Lancaster County died from measles-related causes. A 6-week-old infant was confirmed to have died directly from measles, while a newborn's death was attributed to an internal hemorrhage and a "traumatic rupture" of the spleen. Both infants were too young to be vaccinated, as the first dose of the MMR vaccine is typically administered at around 1 year of age. According to the Pennsylvania health department, a death is considered "measles associated" if there is clinical evidence of measles infection, a positive laboratory test, and if the death occurred within 30 days of the onset of symptoms. After thorough investigations, the state confirmed the two latest deaths were linked to measles. Pennsylvania has reported nearly 700 cases of measles this year, with about 100 new cases reported in the past seven days. On a national level, the Centers for Disease Control and Prevention (CDC) has confirmed 3,294 measles cases as of September 10. However, the CDC has not officially confirmed any of the deaths reported in Pennsylvania and has no records from 2026 indicating that measles was the underlying cause of death. The CDC director noted that Pennsylvania had not requested assistance, though the state health department said it regularly communicates with the CDC and submits daily reports. In the U.S., there have been seven reported measles-associated deaths in the last two years, more than the combined total from the previous three decades. While the country eliminated the domestic spread of measles in 2000, vaccination rates have since fallen below the 95% threshold needed to prevent outbreaks. The Trump administration faced criticism for its handling of vaccine policy, including statements from Health Secretary Robert F. Kennedy Jr., who questioned vaccine safety and reduced funding for local vaccination initiatives. Pennsylvania’s health secretary, Dr. Debra Bogen, expressed her condolences to the families affected by the recent deaths and stressed the importance of ensuring access to the MMR vaccine. The outbreak in the state has been linked to declining vaccination rates, particularly in agricultural areas of Lancaster and Mifflin counties. Other states, including Utah, Florida, Virginia, and Texas, have also reported dozens of measles cases. Globally, measles remains the leading cause of vaccine-preventable infant deaths.