The CDC specialist will work through the agency’s Epi-Aid program, which provides short-term technical expertise to states confronting urgent public health problems. These teams typically assist for one to three weeks. A U.S. Department of Health and Human Services official said the federal government has also provided nearly $4 million in one-time funding for Pennsylvania’s measles response through most of 2027.

State health officials reported Wednesday that 1,222 people in nearly two-thirds of Pennsylvania’s counties had contracted measles so far in 2026. The state recorded 157 additional cases in the past week. Health experts say the reported total may be an undercount because not every case is reported.

Lancaster County remains the outbreak’s center, with 443 cases this year. Mifflin County has reported 183 and Chester County, in the Philadelphia suburbs, has reported 90. About one in five reported cases statewide has required hospitalization.

The federal response comes amid a dispute between state and federal officials over how measles-related deaths are counted. Pennsylvania has reported five confirmed measles-associated deaths; a sixth death reported by a Franklin County coroner is under state investigation. As of Wednesday, the CDC’s national dashboard listed two measles deaths for the year and did not identify where they occurred.

HHS said the CDC is working to establish a standard definition for measles deaths. In the meantime, the agency says it will report deaths when the National Center for Health Statistics identifies measles as the underlying cause, based on state-submitted death records. Public health experts have said that process differs from earlier reporting practices and can take weeks longer.

Pennsylvania officials had said last month they would accept Epi-Aid assistance if the CDC acknowledged the deaths reported by the state. Before making the formal request, state health officials said they were already working with CDC staff. HHS had previously said Pennsylvania had not sought assistance through the program.

The disagreement has become political. HHS Secretary Robert F. Kennedy Jr. has questioned Pennsylvania’s reporting of measles-associated deaths, while Gov. Josh Shapiro has accused Kennedy of spreading misinformation that weakened vaccination rates and left the state more vulnerable to an outbreak. The HHS statement said Kennedy and CDC Director Erica Schwartz recommend vaccination as the most effective way to prevent measles.

Vaccination activity has increased as the outbreak has worsened. Providers administered more than 56,000 measles, mumps and rubella (MMR) vaccine doses in September—more than twice the usual monthly total—and more than 23,000 in the first two weeks of October, according to state health officials.

Pennsylvania’s outbreak is the largest in the country in more than three decades. The CDC said it would continue working with state health officials to support the response and protect public health.