U.S. Measles Cases Hit Highest Level Since Elimination as Pennsylvania Reports Fourth Death

The United States has now recorded more measles cases in 2026 than in any year since the disease was declared eliminated from the country in 2000, with federal health officials reporting a fourth outbreak-linked death in Pennsylvania and no sign that transmission has peaked.

As of Sept. 17, the most recent date for which national figures are available, the Centers for Disease Control and Prevention had confirmed 3,471 measles cases so far this year, an increase of 177 cases, or about 5.4%, from the previous week. Cases have been reported in 47 jurisdictions, and the agency counts 39 separate outbreaks in 2026, with 95% of this year's cases linked to one of those outbreaks rather than occurring in isolation. About 9% of confirmed cases have required hospitalization, and the CDC's outbreak surveillance page shows the pace of new cases has not meaningfully slowed since midsummer.

A fourth death in Pennsylvania

The heaviest toll has fallen on Pennsylvania, where the state Department of Health confirmed two additional measles-associated deaths this month, one in Jefferson County and one in Mifflin County, both involving unvaccinated residents. Those deaths followed two earlier ones in Lancaster County in August, which state officials said were Pennsylvania's first measles deaths in 35 years. All four deaths reported nationally in 2026 have involved unvaccinated individuals, according to state and federal officials, who have not released further identifying details out of privacy concerns.

Nationally, 95% of this year's confirmed cases involve people who were unvaccinated or whose vaccination status is unknown, the CDC says, underscoring that the resurgence is concentrated among communities with lower measles, mumps and rubella vaccination coverage rather than reflecting a broad failure of vaccine protection.

Measles was declared eliminated in the United States in 2000, meaning the virus was no longer circulating continuously within the country, though imported cases have periodically sparked local outbreaks in the years since. Public health researchers have warned that sustained transmission lasting 12 months or more could jeopardize that elimination status, a threshold the current outbreaks are approaching depending on how individual case clusters are ultimately linked.

Measles is among the most contagious viruses known, capable of infecting roughly 90% of susceptible people exposed to it in an enclosed space, and the two-dose MMR vaccine remains about 97% effective at preventing infection. The CDC has continued to recommend the standard childhood schedule, with the first dose at 12 to 15 months and a second between ages 4 and 6, and is urging clinicians in outbreak-affected states to verify vaccination status for patients presenting with fever and rash.

State health departments are expected to issue updated county-level case counts in the coming days, and the CDC typically revises its national totals as delayed reports from state laboratories are confirmed, meaning the true scale of this year's outbreak may not be fully known for several more weeks.