Bolivia's 597 measles cases led South America in the region's worst year since 2020
PAHO counted 14,891 confirmed cases across the Americas in 2025, a 32-fold rise on 2024. Six South American countries reported cases, and only a third of the region's countries reach the coverage that stops outbreaks.
The Pan American Health Organization published a regional situation summary on 27 February reporting 14,891 confirmed measles cases and 29 deaths across 13 countries of the Americas during 2025 — the highest annual count since 2020 and a 32-fold increase over 2024 [s1]. Six South American countries appear in that tally, and the largest of them, Bolivia, reported 597 cases on its own [s1].
What the South American numbers look like
PAHO's country breakdown for 2025 lists the Plurinational State of Bolivia at 597 cases, Paraguay at 49, Argentina at 36, Brazil at 38, Uruguay at 13, and Peru at 5 [s1]. Those figures sit well below the regional heavyweights — Mexico reported 6,428 cases including 24 deaths, Canada 5,436 including two deaths, and the United States 2,242 including three deaths [s1] — but they are notable precisely because they appeared in countries where PAHO describes measles as having been "previously low or absent" [s1].
Transmission carried into the new year. In the first three epidemiological weeks of 2026, the region logged 1,031 cases — a 45-fold increase against the 23 cases recorded in the same weeks of 2025 [s1]. Bolivia contributed 10 of those, and Chile, which reported nothing in 2025, notified a single imported case [s1]. Uruguay reported one. The bulk of the early-2026 count sat in Mexico (740), the United States (171), Canada (67), and Guatemala (41) [s1]. PAHO recorded no deaths in the region as of 28 January 2026 [s1].
Why a few hundred cases in Bolivia matters regionally
The Americas were the first WHO region to interrupt endemic measles transmission, achieving it initially in 2016 and again in 2024 after a period of re-established spread [s1]. That second achievement did not hold: PAHO reports that the 2025 surge led to the re-establishment of endemic transmission in Canada in October 2025, alongside persistent outbreaks in the United States, Mexico and Bolivia [s1].
Bolivia is therefore one of only four countries PAHO names as carrying persistent outbreaks rather than isolated importations — the only South American country in that group [s1]. That distinction matters because regional elimination status is a property of the whole region, not of individual countries. The verification framework treats sustained chains of transmission anywhere in the Americas as a regional problem, which is why a South American outbreak of a few hundred cases sits in the same paragraph as a Canadian outbreak of several thousand.
The immunity picture behind it
Among 11,248 confirmed cases from 2025 and early 2026 with epidemiological information available, PAHO found the highest incidence in children under one year of age, at 6.6 cases per 100,000 population, followed by children aged one to four (3.6 per 100,000) and five to nine (2.1 per 100,000) [s1]. Seventy-one percent of those cases occurred in unvaccinated individuals; vaccination status was unknown for a further 18% [s1].
Regional coverage improved slightly but remains far short of what is needed. First-dose measles-mumps-rubella coverage across the region rose from 87% in 2023 to 89% in 2024, and second-dose coverage from 76% to 79% [s1]. Yet only 15 of 45 countries and territories — 33.3% — reached the 95% first-dose threshold PAHO identifies as the level required to prevent outbreaks, and only nine of 45 (20%) reached it for the second dose [s1].
The transmission classification is equally telling: 16% of cases were classified as imported and 71% as import-related [s1]. In PAHO's reading, that pattern points less to a failure of border control than to what happens after importation — internal spread through populations with accumulated immunity gaps [s1].
What this data does and does not establish
These are confirmed cases reported by member states and compiled regionally, with the usual caveats that attach to surveillance data: countries differ in how aggressively they investigate suspected cases and in their laboratory confirmation capacity, and PAHO's own recommendations emphasise strengthening exactly those functions [s1]. The Canadian figure includes probable as well as confirmed cases, which is footnoted in the source [s1]. The under-one incidence rate is a regional aggregate and does not describe any individual country's infant burden.
Nor does the data explain why Bolivia specifically became the South American focus. PAHO's general explanation — years of accumulated susceptible individuals in vaccine-hesitant, close-knit, highly mobile communities, combined with suboptimal routine coverage, pandemic-era service disruption, and access barriers — is offered for the region as a whole rather than country by country [s1].
What PAHO is asking countries to do
The recommendations are conventional and unsurprising: laboratory-based surveillance for early case identification, rapid response to prevent secondary transmission, targeted follow-up vaccination campaigns to close immunity gaps, and risk communication aimed at countering vaccine misinformation [s1]. PAHO asks countries to identify and prioritise vaccine-hesitant communities and high-risk groups based on cohort susceptibility analysis, and to reach at least 95% two-dose MMR coverage at national and subnational levels [s1] — the subnational qualifier being the one that national averages routinely hide.
What to watch
Whether Bolivia's outbreak is interrupted, and whether the six South American countries that reported cases in 2025 hold at importation-only status through 2026. PAHO's own framing is blunt about the stakes: the current pattern, in its words, demonstrates how quickly progress toward elimination can be reversed when immunity gaps persist [s1].
Sources
- Sustained increase in measles cases prompts the Americas to strengthen surveillance, rapid response and vaccination efforts — Pan American Health Organization / Revista Panamericana de Salud Pública, 27 February 2026
Sources
- Sustained increase in measles cases prompts the Americas to strengthen surveillance, rapid response and vaccination efforts — Pan American Health Organization / Revista Panamericana de Salud Pública , February 27, 2026
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