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The Centers for Disease Control and Prevention (CDC) is working with state epidemiologists to create a standard definition for measles deaths.
The CDC launched the project earlier this summer, before Pennsylvania announced two “measles-associated” deaths, setting off a controversy after the coroner who reviewed the deaths contradicted Gov. Josh Shapiro and the state health department, telling the media that one of the deaths was not caused by measles.
“Pennsylvania may classify deaths as ‘measles-associated’ under its state surveillance definition, but CDC is working with the Council of State and Territorial Epidemiologists (CSTE) to establish a standardized definition for measles deaths to ensure consistent reporting across jurisdictions,” U.S. Department of Health and Human Services Press Secretary Grace Davis Jamison told The Defender.
“CDC will apply the same national standard to every state and report any measles-caused deaths when the National Center for Health Statistics identifies measles as the underlying cause based on death record information submitted by the states,” Jamison said.
On Aug. 25, the Pennsylvania Department of Health announced two deaths, both infants, describing them as “measles-associated.” In mid-September, the state announced two additional deaths, including one of a 40-year-old woman with a long history of underlying illness.
The CDC measles surveillance page, updated today, displays an asterisk with only one recorded death in 2026. The accompanying note says, “This number is subject to change; CDC will update its reporting as additional information becomes available and relevant reviews are completed.”
The federal government recently revised how it counts measles deaths in response to ongoing scrutiny around whether the Pennsylvania fatalities labeled “measles-associated” were actually caused by measles.
The Guardian recently reported the CDC will base its measles death count on data from the National Center for Health Statistics (NCHS).
The CDC updated its site today, only after the NCHS alerted the agency about a measles-related death, Jamison said.
“Through its standard process, NCHS verified that the death occurred and that measles was listed as the underlying cause of death,” Jamison told The Defender.
Previously, the CDC pulled its measles death figures from the National Notifiable Diseases Surveillance System (NNDSS), which receives public health surveillance data from state, local and territorial health departments.
NCHS tracks only the official causes of death as reported on death certificates, while the NNDSS reports include additional information about a person’s health status at the time of their death.
CDC listed Pennsylvania deaths, then removed them
Pennsylvania, meanwhile, has reported four measles-associated deaths, along with 792 confirmed cases and 155 hospitalizations as of Sept. 21.
Pennsylvania defines a measles-associated death as one occurring within 30 days of symptom onset in a person with clinical evidence of infection, a positive laboratory test and no unrelated cause of death. Health officials also consider medical records and evidence of exposure.
The state said it conducted investigations with county coroners before classifying the four deaths. The Pennsylvania Department of Health did not respond to requests for comment from The Defender.
Inside Medicine reported that the CDC initially listed Pennsylvania’s first two deaths before U.S. Health Secretary Robert F. Kennedy Jr. asked CDC Director Erica Schwartz to remove them.
The change highlights the difference between a death being “associated with” measles and measles being listed as its underlying cause.
An associated death may involve complications or secondary infections following measles, while an underlying-cause standard can be more restrictive.
Secondary infections from measles can sometimes lead to death
“Measles-associated death” is a standard designation that the World Health Organization (WHO) and the CDC have used for decades, said Matthew Ferrari, Ph.D., director of the Center for Infectious Disease Dynamics at Penn State.
“It’s the most useful distinction because it is a case that could have been prevented by a measles vaccination, or by early detection and isolation,” Ferrari told The Defender.
“Measles is severely immunocompromising, so it is very often a secondary infection that is the ultimate cause of death,” he added. “That doesn’t change the fact that preventing the measles case would have prevented the secondary infection.”
Ferrari said the definition of a measles-associated death has become more expansive over time as scientists have learned more about measles’ long-term effects on immunity.
He pointed to research by Dutch virologist Rik de Swart showing that the measles virus kills memory immune cells that protect against infections a person has previously fought off. That suggests illnesses long after a measles infection could be traced to the immune damage it caused, Ferrari said.
Proving that this leads to deaths is difficult because such deaths are hard to document, he added.
Research by epidemiologist Michael Mina, M.D., Ph.D., has found a detectable rise in deaths from all causes after measles outbreaks, Ferrari said, though he cautioned that the finding shows correlation, not causation.
Karl Jablonowski, Ph.D., senior research scientist at Children’s Health Defense (CHD), said that deaths caused strictly by measles are rare and that federal agencies bringing more clarity around what constitutes death as an underlying cause is critical.
“‘What is the mortality burden of the current outbreak? Or, should I be afraid?’ Those are two very different questions that could be asked of the same reported death count,” Jablonowski said.
There are so few measles deaths that it is possible and appropriate to include comorbidities when reporting them, Jablonowski said. “An individual can assess their risk based on how similar they are to others whose death is associated with measles.”
He also said the Pennsylvania cases in particular became politicized instead of scientific.
“Gov. Josh Shapiro declared two measles-associated deaths, then proceeded to say ‘vaccine’ 70 times during the press conference. One was born without a heartbeat and a ruptured spleen, and the other was a 6-week-old afflicted with Amish lethal microcephaly,” Jablonowski said.
He added: “Context matters. A political apparatus of state departments of health makes measles deaths politicizable. Requiring death certificates to describe measles as a cause of death in a national measles death statistic adds reliability to the reported number, not detracts from it.”
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Texas measles deaths in 2025 sparked similar controversy
Similar questions emerged during the 2025 West Texas outbreak, when state officials reported two measles-associated deaths in school-aged children.
The CDC continues to list three deaths — the two in Texas and one in New Mexico — for 2025.
In February 2025, a 6-year-old girl died in a hospital after testing positive for measles and developing pneumonia. Her parents later told The Defender that her measles symptoms appeared to be improving while her fever and breathing worsened.
CHD obtained the child’s medical records from the parents. Dr. Pierre Kory, who has extensive experience in pulmonary and critical care medicine, analyzed the records. Kory told CHD.TV, the girl died from a secondary bacterial pneumonia that had “little to do with measles.”
A second child, 8-year-old Daisy Hildebrand, died in April 2025. Texas officials described her death as “measles pulmonary failure.”
However, physicians who reviewed Daisy’s records told The Defender that she died from acute respiratory distress caused by hospital-acquired pneumonia. They said she contracted an antibiotic-resistant E. coli infection during a previous hospital stay.
The Texas cases illustrate why classifying deaths can be complicated. Measles can cause pneumonia and suppress immune function, but patients may also experience bacterial infections, underlying illnesses or complications related to medical care.
A uniform definition could help states classify such deaths consistently.
The CDC had recorded 3,471 confirmed measles cases nationwide as of Sept. 17. Pennsylvania accounted for the country’s largest active outbreak, while Texas, South Carolina and Utah also experienced substantial outbreaks during the resurgence that began in 2025.
The unresolved issue is whether the eventual federal definition will preserve the broader category of measles-associated deaths used by states — or count only deaths for which measles is formally identified as the underlying cause.
Related articles in The Defender
- CDC Revamps System for Counting Measles Deaths, as Pennsylvania Reports Fourth ‘Measles-Associated’ Death
- 40-Year-Old Pennsylvania Woman With ‘Long, Long History’ of Underlying Illnesses Dies After Catching Measles
- Vaccinated People Can and Do Spread Measles, Peer-Reviewed Analysis Finds
- 6-Week-Old Amish Infant With Fatal Genetic Condition Died From Measles, Coroner Confirms
- Coroner Contradicts Pennsylvania Health Officials, Says Measles Didn’t Cause Newborn’s Death
- 2 ‘Measles-Associated’ Deaths in Pennsylvania Spark Media Blitz — But Officials Won’t Release Details
