Pennsylvania health officials reported a fifth measles associated death Wednesday as the state’s outbreak approached 1,000 confirmed cases. The outbreak is on track to become the largest the United States has experienced in decades and has fueled political clashes over how measles deaths are counted.

The Pennsylvania Department of Health said the person who died was unvaccinated and lived in Lancaster County. About 40% of the state’s measles cases have been concentrated in that county.

As of Wednesday, Pennsylvania had recorded 943 cases since the outbreak began in April. At least 176 patients have been hospitalized, and all but four of the cases involved people who were not fully vaccinated.

The department said it would not disclose additional information that could personally identify the person who died. It determined that the death meets the definition of a measles associated death and reported it to the US Centers for Disease Control and Prevention.

Pennsylvania’s four previously reported measles associated deaths involved an unvaccinated teenager from Mifflin County, a woman, age 40, from Jefferson County, and two infants from Lancaster County. The mounting toll has intensified scrutiny of federal and state reporting.

The CDC lists only two measles deaths on its dashboard. However, the agency cautions that “this number is subject to change; CDC will update its reporting as additional information becomes available and relevant reviews are completed.”

Earlier this month, the Pennsylvania Department of Health said it had requested help through the CDC’s Epi-Aid program. Department Secretary Dr. Debra Bogen wrote to CDC Director Dr. Erica Schwartz that Pennsylvania would rescind the request “if CDC is unable to transparently and accurately communicate information about those measles-associated deaths.”

The US Department of Health and Human Services offered a different account, saying the CDC had not received a formal Epi-Aid request from Pennsylvania. The disagreement has added another layer of tension to the response as case numbers and deaths continue to rise.

“If requested, CDC stands ready to deploy epidemiologists to support the state’s identified needs,” HHS press secretary Emily Hilliard told CNN in a statement. She added, “Secretary Kennedy and CDC Director Dr. Erica Schwartz continue to recommend the MMR vaccine as the most effective way to prevent measles infection.”

Pennsylvania Department of Health Press Secretary Neil Ruhland told CNN that discussions with federal officials had not ended. “Conversations between PA DOH and CDC are ongoing regarding our request for an Epi-Aid.”

The United States has not recorded this many measles deaths in decades. The last year with more than four measles deaths was 1991, while last year brought three deaths, including two in Texas and one in New Mexico.

Dr. Stephen Diamantoni, the Lancaster County coroner, said he fears the outbreak could become worse as the seasons change. Diamantoni is also a family physician and described himself as a strong advocate for immunization.

“Measles generally, as well as many other respiratory illnesses, does tend to get worse over the fall and winter months,” Diamantoni told CNN. “So it very well could become much worse.”

Nationwide, nearly 3,700 measles cases have been reported so far in 2026, according to CDC data. The country has not seen this many cases during any year since 1991, surpassing a grim milestone that was reached only last year.

Death from measles occurs in one to three patients for every 1,000 cases. That rate suggests Pennsylvania’s outbreak could be significantly larger than the state’s officially reported case total indicates.