US Measles Cases Hit 1,952 as Country Edges Toward Losing Elimination Status It Has Held Since 2000
The CDC logged 1,952 measles cases through May 21, 2026 — on pace to surpass last year's high not seen since 1992 — as a Lancet study concludes four of seven elimination indicators have already been missed.
Overview
The United States has recorded 1,952 confirmed measles cases in 2026 as of May 21, according to the Centers for Disease Control and Prevention — a total that places the country on pace to surpass 2025’s tally of 2,288 cases, the highest annual count since 1992. A research letter published April 30 in The Lancet concluded that four of the seven CDC indicators for measles elimination have already been missed and that, given the current trajectory, the US is highly likely to lose the elimination status it has held since 2000. A formal PAHO review of that status is scheduled for November.
What We Know
Scale of the 2026 outbreak. The CDC’s latest update, reflecting data through May 21 and published May 22, counts 1,952 confirmed measles infections across 40 jurisdictions. The agency has recorded 29 new outbreaks in 2026, and 93% of confirmed cases (1,815 of 1,952) are outbreak-associated. By comparison, 2025 saw 48 outbreaks and 2,288 total cases across the full year.
Who is being affected. About 92% of 2026 cases are attributed to unvaccinated individuals or those with unknown vaccination status, a pattern consistent with 2025, when roughly 93% of cases occurred in people who were unvaccinated or of unknown status. The 2025 outbreak produced three deaths and 245 hospitalizations, according to Healthline.
The Lancet analysis. A correspondence letter titled “Will the USA lose its measles elimination status?” by Maimuna Majumder, PhD, MPH and Anne Bischops, MD, published April 30, 2026 in The Lancet, examined seven CDC indicators for elimination status and found the US has already missed four of them. The researchers found the country’s measles incidence reached approximately 93 cases per 10 million people in early 2026 — far exceeding the elimination threshold of fewer than one case per 10 million. Only 6-7% of cases originated from abroad since 2025, with the remainder acquired domestically. The estimated transmission rate (Rt) exceeded 1.0 — meaning each case was generating more than one additional infection — more than 75% of the time since early 2025.
“Declining vaccination rates have already been a warning sign that measles could return. However, losing status would be a clear and very concerning indicator,” Bischops said, as reported by Medical Xpress.
Majumder added: “Viral infections aren’t all benign and a measles infection, even when cleared, can result in lifelong problems. Babies less than a year old are among those at greatest risk for severe complications, and the full impact on children exposed during the current outbreak may only show up years later.”
Vaccination rates. MMR vaccination coverage among US kindergartners has declined from 95.2% during the 2019–2020 school year to 92.5% in the 2024–2025 school year, according to the CDC — below the approximately 95% threshold needed to maintain herd immunity. In some Texas counties, vaccination rates have fallen as low as 79-90%, according to Medical Xpress reporting on the Lancet analysis.
PAHO review timeline. The Pan American Health Organization’s Regional Verification Commission will formally evaluate the US’s measles elimination status in November 2026 during its regular annual meeting, PAHO announced on March 2. The review covers a one-year analysis period from January 20, 2025 — the recognized start of the current epidemic. The November timing, PAHO said, allows the US to complete viral genome sequencing and bioinformatics analysis of ongoing outbreak chains before the determination is made.
Regional context. The Americas region had already lost its broader measles-free status in November 2025, after PAHO confirmed that endemic transmission had been re-established in Canada, where the virus circulated uninterrupted for at least 12 months, PAHO reported. The US and Mexico both face similar individual reviews.
Expert voices. Nathan Lo, MD, an assistant professor of medicine at Stanford University, attributed ongoing case counts to “declining vaccination in the U.S. and high measles circulation globally,” noting that measles cases continue to demonstrate sustained circulation in the country, Healthline reported. William Schaffner, MD, an infectious disease specialist and professor at Vanderbilt University, stated: “Vaccination is the way to prevent measles. There are no other ways.”
What We Don’t Know
The Lancet analysis examined four missed indicators out of seven; the status of the remaining three is uncertain. Even if the case trajectory stabilizes, the determination rests with the PAHO commission, which evaluates data holistically and also weighs whether domestic transmission can be shown to be genetically linked to a limited set of imported chains — the question the US genome-sequencing effort is intended to answer.
It is also unclear whether ongoing case counts will stabilize before the summer travel season, a period that historically correlates with increased exposure risk as international travel volumes rise.
Analysis
The US achieving measles elimination in 2000 was one of the central public health achievements of the modern vaccination era, and losing that status would mark a visible reversal. Even if the formal PAHO designation were later restored through intensified vaccination, the practical consequence — sustained endemic transmission in a country that eradicated domestic spread a quarter century ago — would already be in evidence.
The underlying driver is well-established: national MMR coverage has slipped to 92.5%, and localized exemption clusters, particularly in Texas and Utah, have created pockets where the virus can sustain chains of transmission. Measles requires roughly 95% population immunity to prevent sustained spread, as Medical Xpress reports citing the Lancet analysis. The gap between those figures has proved sufficient for large, sustained outbreaks to take hold.
The November PAHO review is not a final verdict — the US can still demonstrate through genomic sequencing that outbreaks trace to a limited number of imported sources rather than endemic circulation. But with four of seven elimination indicators already missed and the transmission rate above the endemic threshold for most of the past year and a half, the epidemiological data already tell a clear story.