The United States has reported 5,182 confirmed measles cases in 2026, marking the highest number of infections for the highly contagious disease since 1991, according to data released by the Centers for Disease Control and Prevention (CDC). The current year's figures represent more than double the 2,289 cases recorded in 2025.

This surge in measles cases occurs amid a concerning decline in vaccination coverage among US kindergarteners. Coverage dropped from 95.2 percent in the 2019-2020 school year to 92.4 percent in the 2025-2026 school year. Measles, a virus that can be prevented by vaccination, is known for its high transmissibility.

Children and teenagers account for nearly 60 percent of the confirmed cases this year. Specifically, children under five years old represent 18 percent of cases, while those aged five to 19 comprise 41 percent. The majority of these infections, totaling 4,993, were associated with outbreaks.

The implications of this resurgence are significant, particularly given that the US declared measles eliminated more than two decades ago. The increase in cases globally, especially in communities with lower vaccination rates, suggests a broader challenge in maintaining herd immunity against vaccine-preventable diseases.

A dispute has emerged regarding the national death toll attributed to measles. While the CDC data indicates four measles-related deaths in 2026, state officials, particularly in Pennsylvania, have reported higher numbers. Pennsylvania's Department of Health documented six deaths and 1,487 cases, with state officials classifying deaths as "measles-associated" if a confirmed case results in fatality within 30 days, barring unrelated causes.

This discrepancy has led to a debate between Pennsylvania Governor Josh Shapiro and US Health Secretary Robert F Kennedy Jr. The CDC initially included two deaths reported by Pennsylvania in its national tally but later removed them after Secretary Kennedy questioned the direct causality of measles in those fatalities. Experts note that tracking "measles-associated" deaths is a standard epidemiological practice used by both the World Health Organization and the CDC.

Infectious disease experts have expressed concern that the disagreement over classifying measles deaths could undermine established public health tracking methods. They emphasize that a standardized definition for measles-related fatalities is crucial for accurate monitoring and response to outbreaks. The CDC has stated it is collaborating with the US Council of State and Territorial Epidemiologists to develop such a standardized definition.

The rise in measles cases and the controversy surrounding death classification highlight challenges in public health communication and the importance of sustained high vaccination coverage. The situation also raises questions about the potential impact of vaccine skepticism on public health efforts and the ability to maintain disease elimination status.