The Centers for Disease Control and Prevention reported 4,410 measles cases nationwide as of October 15, an increase of 330 from its previous update a week earlier. The highly contagious disease has also led to 451 hospitalizations across the country this year, according to federal data.

Pennsylvania has emerged as a major center of the outbreak, reporting 1,222 cases as of October 14, along with 225 measles-related hospitalizations, according to the state health department. The CDC announced Tuesday that it would provide additional support to Pennsylvania to help investigate and respond to the spread of the disease.

The death toll has also drawn attention, with conflicting figures appearing in state and federal reporting. Pennsylvania has reported five measles-related deaths this year, while the CDC has confirmed two measles-associated deaths in 2026 without identifying the states involved.

The discrepancy follows a change in the CDC’s reporting methodology last month. The agency shifted to using mortality data from the National Center for Health Statistics to track measles-related deaths rather than relying on reports from state health departments. The change has drawn scrutiny as officials attempt to establish a clearer picture of the outbreak’s toll.

Children and teenagers between the ages of 5 and 19 account for the largest share of reported infections, with 1,856 cases, or approximately 42% of the national total. Adults aged 20 and older make up another 1,787 cases, representing about 41%, according to CDC figures.

The spread of measles has prompted emergency measures elsewhere. Earlier this month, New York declared a disaster emergency in response to its outbreak, becoming the first U.S. state to issue such a declaration over the disease.

Measles is highly contagious and can cause serious complications, particularly among young children and other vulnerable individuals. The rising case count and hospitalizations have increased pressure on public health authorities to contain outbreaks and provide accurate information about the disease’s spread and severity.

With cases continuing to rise, federal officials are expanding their response in Pennsylvania while state and national health agencies monitor infections, hospitalizations, and deaths. The latest figures underscore the scale of the outbreak as the CDC and state authorities work to limit further transmission.