A-Z Index × Submit A-Z Index × Submit A-Z Index Search Dropdown × Submit Facebook Twitter LinkedIn Syndicate Emerging Infectious Disease journal ISSN: 1080-6059 Disclaimer: Early release articles are not considered as final versions. Any changes will be reflected in the online version in the month the article is officially released.
As measles elimination unravels across the Americas, Europe, and the Western Pacific, Japan is experiencing a resurgence of measles; the World Health Organization had verified elimination of measles in Japan in 2015. By epidemiologic week 20 of 2026, a total of 498 cases had been reported, exceeding every full-year total since 2020. Median case-patient age has fallen to 26 years, shifting the burden from a generation who received single-dose measles vaccinations to younger cohorts caught between successive vaccination-policy transitions. Among case-patients with a documented 2-dose vaccination history, more than half experienced modified measles, an attenuated, easily missed illness that delays diagnosis and isolation. As mass gatherings concentrate global travel, Japan has become a sentinel for the fragility of measles elimination, including in countries that consider elimination status secure. Surveillance shows importation-driven resurgence; the shift in genotype profile from D8 to B3 predominance back to D8 enabled tracking of source countries.
In November 2025, the World Health Organization (WHO) Region of the Americas lost its regional elimination status after endemic transmission was reestablished in Canada, which had maintained elimination since 1998 ( 1 ). Transmission has since accelerated: by epidemiologic week 28 of 2026, the region had reported 47,459 confirmed cases and 44 deaths, >3 times the 2025 total and the highest count since 2004 ( 2 ). The Pan American Health Organization (PAHO) Regional Verification Commission, which reviews all countries in the region annually, will consider the 2026 reports, including that of the United States, in November 2026 ( 1 , 3 ). By September 10, 2026, the United States had recorded 3,294 confirmed cases, its largest annual total since elimination was declared in 2000; of the cases, 95% were outbreak-associated and 95% occurred in unvaccinated persons or those of unknown status ( 4 , 5 ). The percentage internationally imported has fallen to ≈10%, signaling a shift toward sustained domestic transmission ( 3 ).
The erosion of measles elimination status is not confined to the Americas. The WHO European Region recorded 127,350 measles cases in 2024, double the 2023 total and the highest in >25 years ( 6 ); on the basis of that resurgence, WHO announced in January 2026 that 6 countries, including the United Kingdom, had lost their elimination status. The age structure for those cases is instructive: among cases reported in Europe during January–June 2026, half (51%) were among those > 15 years of age, and 15% of those with known vaccination status had received 1 dose ( 7 ).
Japan’s own region is a cautionary backdrop. Measles in the WHO Western Pacific Region rose 743% during 2022–2024; Mongolia and Cambodia, the first middle-income countries there to eliminate measles, later lost that status to importation-related outbreaks ( 8 , 9 ). Japan, where elimination was verified in 2015 ( 10 ), had recorded more cases by mid-2026 than in any full year since 2020. We argue that Japan is a sentinel for an elimination framework under growing strain, with lessons exte…