The CDC’s measles page was updated Wednesday, Sept. 23, to show one U.S. measles death so far in 2026, with a note that the number may change as more information comes in, NBC News (opens in new tab) and The Philadelphia Inquirer (opens in new tab) reported. Pennsylvania’s Department of Health has separately reported four measles-associated deaths over the past month, two infants and two adults, according to CIDRAP (opens in new tab), NBC News (opens in new tab) and the Inquirer; the department's Sept. 21 news release listed four confirmed measles-associated deaths.

The two numbers rest on different definitions. The CDC counts a death after the National Center for Health Statistics (NCHS) confirms through death records that it occurred and that measles was listed as the underlying cause, according to a federal statement reported by the Inquirer and NBC News (opens in new tab). Pennsylvania counts a “measles-associated death” when a person with clinical signs of measles and a positive laboratory test dies within 30 days of symptom or rash onset and the death is not due to an unrelated cause, such as a car crash, according to the state health department.

CIDRAP (opens in new tab) described the NCHS requirement as an unusual step, since NCHS data are normally used to track longer-term mortality trends, and said it has delayed federal recognition of the Pennsylvania deaths. The Inquirer reported that former CDC officials say the agency previously confirmed deaths through a separate disease-surveillance system and that NCHS records can take weeks. The CDC says it is working with the Council of State and Territorial Epidemiologists on a standard definition of a measles death.

At the time, it was not known whether the single CDC-listed death was one of Pennsylvania’s. A Pennsylvania spokesperson said the state did not know which death the CDC was counting, and the CDC declined to identify the person or location, according to NBC News (opens in new tab) and the Inquirer. Before the page update, CIDRAP (opens in new tab) reported that the CDC’s weekly update had not acknowledged any of the four Pennsylvania deaths. The CDC confirmed three measles deaths in 2025, CIDRAP (opens in new tab) and NBC News (opens in new tab) noted.

At the time, the national count stood at 3,471 cases across 45 states plus New York City and Washington, D.C., after 177 cases were added in the latest weekly update, CIDRAP (opens in new tab) reported. About 9% of patients, more than 300 people, have been hospitalized, and 95% were unvaccinated or had unknown vaccination status.

Pennsylvania has the country’s largest outbreak. NBC News (opens in new tab) reported that as of Wednesday, Sept. 23, the state health department counted 835 cases and 164 hospitalizations this year. In a Sept. 21 news release, the department had reported 792 cases and 155 hospitalizations.

As of Wednesday, Sept. 23, the CDC listed one U.S. measles death under its standard, which requires death records to list measles as the underlying cause, while Pennsylvania reported four under its definition of a death within 30 days of illness in a lab-confirmed case.

Update, Oct. 1: The CDC raised its national count to two measles deaths in 2026 late Monday, Sept. 28, without identifying the person who died or saying where the death occurred, The Washington Post reported in a story published by The Philadelphia Inquirer (opens in new tab). “Through its standard process, NCHS verified that the death occurred and that measles was listed as the underlying cause of death,” Health and Human Services spokesperson Emily Hilliard said, according to the Post. On Sept. 30, Pennsylvania’s Department of Health reported a fifth measles-associated death, an unvaccinated Lancaster County resident, and said confirmed cases had reached 943 across 39 counties, with 176 hospitalizations. CNN (opens in new tab) reported the same figures and said the CDC’s dashboard counted two deaths, with a note that “this number is subject to change; CDC will update its reporting as additional information becomes available and relevant reviews are completed.” It is unclear whether either of the CDC-counted deaths is one of Pennsylvania’s. CNN (opens in new tab) also reported that nearly 3,700 measles cases have been reported nationwide so far in 2026, according to CDC data.