Pennsylvania measles outbreak becomes largest and deadliest in 30 years

Pennsylvania is experiencing the largest and deadliest measles outbreak in the United States in over 30 years. Since April, the state's Department of Health has reported 1,066 cases and five deaths, with more than 200 hospitalizations.

The outbreak is centered in Lancaster County, though cases have been identified in more than half of the state's counties. The scale of this event surpasses recent significant outbreaks in Texas and South Carolina. Data indicates that the vast majority of those infected were unvaccinated; less than 1% of the 1,066 reported cases had received the measles, mumps, and rubella (MMR) vaccine.

Nationally, the CDC reports at least 3,887 measles cases in 2026, the highest annual figure since 1991. While measles was declared eliminated in the U.S. in 2000, the Pan American Health Organization is currently reviewing that status. There is ongoing discussion regarding death counts, as the CDC has currently recorded two measles-related deaths for 2026, while state officials report five, leading to questions regarding the definition of deaths associated with the disease.