The Americas lost measles elimination in November 2025, and the United States is judged in November 2026

The line repeated most often is that the United States is about to lose its measles elimination status. The documents are more precise, and the precision is the story: there is a defined criterion, a defined analysis period and a defined date on which a defined body will decide.

The regional decision has already been made. The Measles, Rubella and Congenital Rubella Syndrome Elimination Regional Monitoring and Re-Verification Commission met in Mexico City from 4 to 7 November 2025. It found that endemic measles transmission had been re-established in Canada, the virus having circulated for at least 12 months. On 10 November 2025 the Pan American Health Organization announced that the Region of the Americas had lost its verification as free from endemic measles transmission. In his remarks at the press briefing that day, PAHO director Jarbas Barbosa said that endemic transmission of measles has been reestablished in Canada, and consequently the Region of the Americas has lost its verification as free from endemic measles transmission. He added that the 34 countries in the Americas maintain their measles free verification, which is the point most coverage dropped: the regional status fell, individual country statuses did not.

The scale behind that decision, as at 7 November 2025, was 12,596 confirmed cases across ten countries and 28 deaths, of which 23 were in Mexico, three in the United States and two in Canada. About 95 per cent of cases were concentrated in Canada, Mexico and the United States, and the regional total was a thirtyfold increase on 2024. Eighty nine per cent of cases were in people who were unvaccinated or whose vaccination status was unknown. Regional coverage with a second dose of measles containing vaccine averaged 79 per cent against the 95 per cent PAHO says is needed to prevent outbreaks. Barbosa described the loss as a setback but also reversible.

The mechanism for the United States was set out by PAHO in an update published on 2 March 2026. The review of measles elimination status in the United States and in Mexico will take place in November 2026, during the Commission's regular annual meeting, rather than at a specially convened session. The analysis periods run from the onset of outbreak, 20 January 2025 for the United States and 1 February 2025 for Mexico. The criterion the Commission applies is uninterrupted circulation of the same virus genotype and lineage for 12 months or more in a specific geographic area. For the United States the analysis incorporates complete viral genome sequencing and a bioinformatics platform for evaluating the molecular data, which means the question is not simply whether cases continued but whether the same lineage did.

The American numbers have kept climbing. CIDRAP at the University of Minnesota reported on 6 August 2026 that the United States had recorded 2,465 confirmed cases in 2026, the highest since 1991, against 2,289 in the whole of 2025, with 94 new cases that week, 93 per cent of patients unvaccinated or of unknown status, 68 per cent aged 19 or under, and 38 active outbreaks. The United States achieved elimination in 2000 and held it for 26 years. Noel Brewster, chair of the national committee that reviews the data, told CIDRAP that these data are public and show a runaway train, and identified an outbreak in Utah lasting more than 12 months as the main criterion for loss of elimination. He also said the United States clearly has a measles problem, as do Canada and Mexico.

The sequence is administrative and slow. CIDRAP reported on 13 August 2026 that the country had seen 20 consecutive months of cases, with measles reported every week since January 2025, and that the national verification committee would conduct its annual review in August, with the formal decision announced in November. The committee reviews, PAHO's Commission decides.

Several things remain unresolved. The Commission's own report from the November 2025 Mexico City meeting was not published at a public address that could be opened for this article, so its reasoning on Canada is known only through PAHO's summary of it. Whether the Utah chain that Brewster identified is the same genotype and lineage throughout, which is what the criterion actually requires, is a laboratory question that has not been reported in the documents available. And nothing in the criteria addresses the harder matter underneath the arithmetic: regional second dose coverage at 79 per cent is 16 points below the threshold PAHO itself sets, and no verification decision in November will change that number.