A sign is posted outside a Pennsylvania Department of Health measles vaccination clinic located in Lancaster County in Peach Bottom, Pa., Tuesday, Oct. 20, 2026. Matt Rourke/AP hide caption

Matt Rourke/AP

The U.S. is grappling with its worst resurgence of measles in decades, with cases particularly high in the state of Pennsylvania.

New data from the U.S. Centers for Disease Control and Prevention shows there have been more than 4,580 measles cases across the U.S. since Oct. 22, which is more than double the number for the whole of 2025.

The vaccination status of 96% of those who contracted measles in 2026 was "Unvaccinated or Unknown," according to data from the CDC.

A measles outbreak across Pennsylvania has grown as officials urge residents to get fully vaccinated against the disease.

At least 1,338 cases of measles have been confirmed in 44 counties across the state so far this year, according to the Pennsylvania Department of Health on Friday. There were 21 new measles cases as of Oct. 21.…