According to the US Centers for Disease Control and Prevention (CDC), the United States has recorded 4,410 measles cases in 2026, an increase of 330 from a week earlier. The CDC has also dispatched an investigator to Pennsylvania to help contain the nation's largest outbreak.
CDC data shows 451 measles-related hospitalizations nationwide this year. Children and adolescents aged 5 to 19 account for 42 percent of cases, followed by people 20 and older at 41 percent. Children under 5 make up 17 percent of cases.
As of Wednesday, Pennsylvania reported 1,222 cases across 42 counties, including 86 new infections since October 9, according to the state health department. The outbreak has led to 225 hospitalizations and five deaths confirmed to be linked to measles. State officials are actively investigating a sixth reported death.
The CDC is sending an expert known as a "disease detective" from its Epidemic Intelligence Service to work with state health officials on the Pennsylvania outbreak. The deployment follows Pennsylvania's request for federal assistance, known as an Epi-Aid.
Pennsylvania has expanded vaccination efforts in affected communities. State health center staff have administered more than 5,900 doses of the measles-mumps-rubella (MMR) vaccine at 202 mobile vaccination sites since the outbreak began in late April.
New York Governor Kathy Hochul declared a statewide disaster emergency on October 5 as measles cases rose in neighboring Pennsylvania. The order, in effect through November 4, expands the pool of health care workers allowed to administer vaccines and gives nurses more flexibility in ordering measles tests.
According to CDC data, measles vaccination coverage among US kindergartners has fallen from 95.2 percent in the 2019-2020 school year to 92.4 percent in the 2025-2026 school year. The agency estimates that about 280,000 kindergartners are at risk because of the vaccination coverage gap.
