The Centers for Disease Control and Prevention (CDC) reported 3,471 measles cases in the U.S. as of September 17, 2026. This marks a 5.37% increase from the previous week, with 177 new cases. Last week, the federal agency reported 3,294 confirmed cases, continuing a trend of surging numbers from the prior week.
The CDC noted that 47 jurisdictions across the country reported 3,454 cases, while 17 cases were among international visitors. These jurisdictions span from Alabama to Wyoming, highlighting the widespread nature of the outbreak.
Pennsylvania Faces Deadly Outbreak
Pennsylvania is grappling with its worst measles outbreak in decades. The state reported its fourth measles-related death this week, an 18-year-old from Mifflin County who died from acute disseminated encephalomyelitis (ADEM). The Mifflin County coroner confirmed the cause of death as complications from measles, though no further details about the teen were disclosed by officials.
The state’s Department of Health recorded 731 cases in 38 of its 67 counties as of September 16, 2026. This represents a significant increase from late August, when 393 cases were reported in 28 counties, indicating an over 300-case surge in just a few weeks. Pennsylvania now has one of the largest numbers of cases in the country.
Pennsylvania’s outbreak has also claimed the lives of two infants: a newborn who died shortly after birth and a 6-week-old. Additionally, a 40-year-old unvaccinated woman from Jefferson County succumbed to the disease, as announced by the local coroner.
Measles Cases Reach 35-Year High
The U.S. has confirmed more measles cases in 2026 than in any year since 1991. As of July 22, 2026, the Johns Hopkins University measles tracker counted 2,295 cases, surpassing the 2,289 cases reported in 2025. This marks the highest annual total since measles was declared eliminated in the U.S. in 2000.
The CDC reported 39 new outbreaks in 2026, with 95% of confirmed cases (3,296 of 3,471) linked to these outbreaks. Of these, 1,920 cases stem from outbreaks in 2026, while 1,376 are from outbreaks that began in 2025.
CDC Changes Death Reporting Method
The CDC has changed its method for reporting measles deaths, now relying on data from the National Center for Health Statistics. This system does not confirm individual cases, making future death reports unlikely. The change means the CDC’s tracker will no longer reflect measles-related fatalities, even as cases continue to rise.
The cumulative number of measles outbreaks, defined as 3 or more related cases, is reported by the CDC, though states hold the most up-to-date information on cases within their jurisdictions. As the situation evolves, continued monitoring and public health interventions remain essential to controlling the outbreak.
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