Sustained increase in measles cases prompts the Americas to strengthen surveillance, rapid response and vaccination efforts

3 February 2026, Washington, D.C. —

During 2025, the Region of the Americas experienced a sharp increase of measles with a total of 14 891 confirmed measles cases, including 29 deaths, reported in 13 countries (Figure 1). This marks the highest annual case count since 2020 and a 32-fold increase compared with 2024 (Figure 2). Cases were reported in countries where measles had been previously low or absent, including Argentina (n=36), Belize (n=44), the Plurinational State of Bolivia (n=597), Brazil (n=38), Canada (n=5 436; including two deaths), Costa Rica (n=1), El Salvador (n=1), the United States of America (n=2 242; including three deaths), Guatemala (n=1), Mexico (n=6 428; including 24 deaths), Paraguay (n=49), Peru (n=5), and Uruguay (n=13) (Figure 1). Despite intensified surveillance and vaccination efforts, the increase in cases throughout the Region led to the reestablishment of endemic measles transmission in Canada in October 2025 and by persistent outbreaks in the United States, Mexico and Bolivia.

Figure 1. Confirmed measles cases^* by epidemiological week of rash onset or notification and by country in the Region of the Americas, 2025–2026 (up to EW 3).

^*Note: Includes confirmed and probable cases for Canada.

Source: Adapted from data reported by the respective countries.

Figure 2. Confirmed measles cases^* by year in the Region of the Americas, 2025–2026 (up to EW 2).

Source: Adapted from the Pan American Health Organization. Number of Vaccine-Preventable Disease (VPD) Cases in the Americas. Washington, D.C.: PAHO/WHO; 2026 [Accessed 26 Jan 2026]. Available from: https://ais.paho.org/phip/viz/im_vaccinepreventablediseases.asp and Pan American Health Organization. Measles/Rubella Weekly Bulletin. Washington, D.C.: PAHO/WHO; 2026 [Accessed 26 January 2026]. Available from: https://www.paho.org/en/measles-rubella-weekly-bulletin

This trend appears to be continuing during the first three epidemiological weeks of 2026. Six of the 13 countries that reported cases in 2025 continued to report cases, and an additional country that had not reported cases in 2025 (Chile) reported an imported case. The total number of cases reported (n=1 031) during these weeks represents a 45- fold increase compared with the 23 cases recorded during the same period in 2025. Cases were notified by Bolivia (n=10), Canada (n=67), Chile (n=1), the United States of America (n=171), Guatemala (n=41), Mexico (n=740), and Uruguay (n=1), presenting continued active transmission in several settings. No deaths have been recorded as of 28 January 2026.

Among 11 248 confirmed cases reported during 2025–2026 with available epidemiological information, the highest incidence rates were observed in children under one year of age (6.6 cases per 100 000 population), followed by children aged 1–4 years (3.6 per 100 000) and 5–9 years (2.1 per 100 000) (Figure 2). Of these cases, 71% occurred in unvaccinated individuals, while vaccination status was unknown in 18%. Sixteen percent were classified as imported, and 71% were import-related, underscoring the role of further internal spread and immunity gaps in starting and upholding outbreaks.

Regional coverage with the first and second doses of the measles, mumps, and rubella (MMR) vaccine slightly increased in 2024 compared with 2023, from 87% to 89% for MMR1 and from 76% to 79% for MMR2. Despite this improvement, only 33.3% (15/45) of countries and territories achieved ≥95% coverage with the first dose, the level required to prevent outbreaks, and only 20% (9/45) reached this threshold for the second dose. Coverage remains uneven, with under or un-vaccinated communities susceptible to infection.

The accumulation over many years of susceptible individuals in specific vaccine-hesitant, close-knit communities with high mobility– combined with suboptimal routine vaccination coverage, disruptions of health services during the COVID-19 pandemic, and challenges in access to vaccination–has created favorable conditions for sustained measles transmission. The disproportionate burden among infants under one year of age further reflects the indirect effects of community immunity gaps, as this group relies primarily on population-level protection.

The continued occurrence of importation-related outbreaks in multiple countries highlights the Region’s vulnerability in the context of increased population mobility. While endemic measles transmission had previously been interrupted in the Americas, initially in 2016 and then in 2024, the current epidemiological pattern demonstrates the fragility of this achievement in the absence of uniformly high vaccination coverage.

PAHO recommends implementing enhanced surveillance and case investigation, including laboratory-based surveillance for early case identification, along with strengthened community engagement and institutional coordination. Countries should also conduct rapid responses to prevent secondary transmission, bridge gaps in vaccination coverage, and enhance capacities at the community and local levels to ensure timely case detection. Moreover, strengthening risk communication and community engagement strategies is also critical to counter vaccine misinformation, increase vaccination uptake, and promote timely medical care to prevent complications and deaths. Differentiated actions for countries with ongoing outbreaks, without outbreaks, countries at risk of importation and priority population groups are outlined in the PAHO Epidemiological Alert.

Maintaining elimination of measles in the Americas requires sustained political commitment, adequate financing, and coordinated regional action. The current epidemiological situation serves as a reminder that progress toward elimination can be rapidly reversed when immunity gaps persist.

Key takeaways:

• The sustained increase in measles cases in 2025 and early 2026 led to the reestablishment of endemic measles transmission in the Region, and underscores the urgent need to strengthen the rapid response to measles cases, enhance surveillance systems capable of rapid case detection and laboratory confirmation, improve routine immunization services and implement targeted follow-up vaccination campaigns to close immunity gaps. Enhanced surveillance, including timely investigation of suspected cases, laboratory confirmation and genotyping, remains essential to monitor transmission dynamics and guide response strategies.

• Countries are encouraged to identify and prioritize vaccination of vaccine hesitant communities, and high-risk groups, based on cohort susceptibility and risk analysis; ensure $\geq 95 \%$ coverage with two doses of MMR vaccine at national and subnational levels; and address challenges in access to immunization services.

• Strengthening risk communication and community engagement strategies is also critical to counter vaccine misinformation and improve demand for vaccination.

Funding Statement

PAHO.

Data availability statement.

Data available from Epidemiological Alert on Measles in the Americas.