The CDC officer is expected to arrive Monday through the agency’s Epidemic Intelligence Service, state officials said Friday. The assistance is intended to help identify how measles is spreading and assess the outbreak’s reach, including cases that may not have been reported.

Pennsylvania reported 1,260 measles cases this year as of Friday, including 121 in the past week. The outbreak has reached 43 of the state’s 67 counties. Lancaster County has recorded 452 cases, Mifflin County is nearing 200, and Chester County has reported 91.

The state has confirmed five measles-associated deaths and is investigating a sixth death reported by a local coroner earlier this week. The CDC’s national measles dashboard, by contrast, lists two measles deaths and does not identify where they occurred.

In a letter Friday to CDC Director Erica Schwartz, Pennsylvania Health Secretary Debra Bogen asked the agency to acknowledge the state-reported deaths and explain how it tracks measles fatalities. Bogen wrote that failing to recognize the deaths “obscures the seriousness” of measles and its toll in the United States. She also said the discrepancy risks undermining public trust in state and federal health agencies.

Pennsylvania defines a measles-associated death as one occurring within 30 days of symptoms in someone with clinical evidence of infection and a positive laboratory test, when another unrelated cause does not explain the death. State officials say all five deaths they have confirmed meet that standard. The sixth case remains under investigation.

The federal assistance follows months of tension between Gov. Josh Shapiro and Health and Human Services Secretary Robert F. Kennedy Jr. Shapiro has accused Kennedy of spreading anti-vaccine misinformation; Kennedy has questioned the state’s handling of at least one reported death. The state says it had already been meeting remotely with CDC staff and formally requested the Epi-Aid on Oct. 7.

Bogen’s letter also asked why the CDC changed its reporting process for measles-associated deaths, a change she said can add weeks to the timeline. She wrote that state officials submitted death information through the updated process several weeks ago and asked why the cases had not appeared on the CDC website.

The state’s request for help and its demand for federal recognition of the deaths remain intertwined. Bogen said CDC leadership must demonstrate good faith before Pennsylvania requests further formal assistance, describing accurate reporting as an important step toward restoring trust. The CDC officer is expected to provide technical assistance for one to three weeks.

About 300 Pennsylvania health department employees, including 60 disease investigators, are working on the outbreak, state officials said. Health care providers have also doubled the number of measles, mumps and rubella vaccinations they typically administer in recent months.

The scale of the outbreak makes accurate case and death reporting consequential for public health planning: officials rely on shared information to understand where infections are occurring and to direct response efforts. Pennsylvania officials say they are seeking the CDC’s expertise while insisting that the public record reflect the deaths reported by the state.