Amid the largest U.S. measles epidemic in decades, a controversy has emerged over how to count measles deaths. From August through October 15, Pennsylvania has reported a total of six measles deaths, but the Centers for Disease Control and Prevention (CDC) has recognized only two in its official statistics.
The CDC announced in early September that it would change its counting method, no longer relying solely on state health department reports. Instead, it will use official death records from the National Center for Health Statistics (NCHS), a sub-agency within the CDC.
Two Systems, Different Purposes
This shift has drawn attention to two federal public health surveillance systems: the Nationally Notifiable Disease Surveillance System (NNDSS) and the National Vital Statistics System (NVSS).
The NNDSS is a collaboration between CDC and jurisdictions across the country that supports sharing and monitoring public health information for a set of diseases and conditions of national interest. NNDSS has roots extending to a system established in 1893 by Congress for jurisdictions to report cases of disease to the Surgeon General. Over time the system expanded, with responsibility for overseeing the system transferred to CDC in 1961. Local and state public health departments have the authority and responsibility to track cases of disease, typically through reporting from health care providers, laboratories, and other sources. In turn, jurisdictions then may provide case information to CDC through NNDSS.
The NVSS, on the other hand, is focused on collecting longer-term, retrospective data on deaths and providing final determinations regarding the cause(s) of death though not necessarily designed for real-time tracking.
Pennsylvania’s Measles Deaths
On August 25, Pennsylvania Governor Josh Shapiro announced the state’s first measles-related deaths since 1992. The Pennsylvania Department of Health (PA DOH) reported these deaths as “measles-associated” to the CDC via the NNDSS, following standard protocol for infectious diseases of national interest.
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However, Secretary of Health and Human Services (HHS) Robert F. Kennedy, Jr. initially objected to Pennsylvania’s classification, calling it “premature.” After the Lancaster County coroner confirmed measles as a contributing cause, Kennedy recognized only the second infant’s death. He stated that the NCHS had no records indicating measles as the underlying cause of death for 2026.
The CDC later changed its policy, stating it would report measles deaths only when the NCHS reports measles as the underlying cause. As of October 15, the CDC’s measles outbreak tally reports two deaths for 2026, with a note saying: “This number is subject to change; CDC will update its reporting as additional information becomes available and relevant reviews are completed.”
On September 30, the Pennsylvania Department of Health confirmed a fifth death and a sixth death was announced by the Franklin County Coroner on October 12.
The Role of NNDSS and NVSS in Death Reporting
Each of these has a long history, dating back to the early 20th century, but serves different purposes. These systems are described below (see Table 1).
Key characteristics of NNDSS include: A set of approximately 120 diseases and conditions that are designated by CDC as “nationally notifiable,” meaning the agency requests state and local health departments report to CDC when new cases of any of these conditions are identified. Measles is a nationally notifiable disease, and has been since 1912. Importantly, CDC cannot require jurisdictions to report case information, but all do, especially for high consequence infectious diseases such as measles.
CDC itself says “since continuous endemic measles transmission has been eliminated, measles is an immediately notifiable disease.” For each NNDSS disease or condition there is a pre-established definition that jurisdictions can consult to help determine if a notifiable case has occurred. These case definitions assure a level of standardization across jurisdictions. The definitions for nationally notifiable diseases are developed in collaboration with the Council of State and Territorial Epidemiologists (CSTE) and intermittently updated and refined. The current NNDSS case definition for measles dates to 2013. Jurisdictions determine the extent of detail provided in their reports.
