Measles — a vaccine-preventable disease that the Pan American Health Organisation declared eliminated from the Americas in 2016 — has recorded 20,521 confirmed cases across 16 countries in the first five months of 2026, according to the latest PAHO epidemiological review. The figure surpasses the full-year total of 15,152 cases recorded across the region in 2025, and has arrived alongside 25 deaths.
Mexico accounts for the majority of cases with 10,920, followed by Guatemala with 6,209, the United States with 1,952 and Canada with 1,018. Public health experts say the resurgence reflects declining vaccination coverage driven by misinformation, healthcare disruption, immigration enforcement effects on preventive care-seeking, and the cumulative toll of years of under-investment in routine immunisation infrastructure.
The Numbers and What They Represent
The Pan American Health Organization has released an updated epidemiological review of measles activity in the Americas region. A total of 20,521 measles cases were confirmed in the Americas region, including 25 deaths, in the first five months of the year in 16 countries. Mexico has the highest case count so far this year with 10,920, followed by Guatemala at 6,209, the United States at 1,952 and Canada at 1,018. To compare, in 2025, 15,152 measles cases were confirmed in the Americas region, including 29 deaths.
The 2026 figures have already outpaced the entire previous year with seven months of the year still remaining. At the current trajectory, total cases for 2026 could significantly exceed 40,000 — a level not seen in the Americas since the pre-elimination era.
Measles was declared eliminated from the Americas in 2016 — meaning the disease was no longer continuously transmitted within the region, with cases occurring only as importations from other parts of the world. The scale and sustained nature of the 2026 outbreak — with community transmission occurring across multiple countries simultaneously — represents the most serious challenge to that elimination status in the region’s history.
What Is Driving the Surge
The resurgence of measles across the Americas is not a single-cause phenomenon. It reflects the convergence of several trends that public health experts have been warning about for years.
Vaccination coverage against measles — achieved through the MMR (measles, mumps and rubella) vaccine — needs to remain above 95% to maintain herd immunity and prevent community transmission. Across much of Latin America and in pockets of the United States and Canada, coverage has fallen below that threshold, creating communities where measles can spread rapidly when an infected individual introduces the virus.
The decline in vaccination rates has multiple drivers. Vaccine hesitancy — amplified by misinformation spread through social media — has reduced uptake in communities across North America and parts of Latin America. Healthcare system disruptions during the COVID-19 pandemic produced a cohort of children who missed routine vaccinations and have remained unprotected. In the United States, immigration enforcement actions have reduced the willingness of undocumented families to seek preventive healthcare — including routine vaccinations — out of fear of enforcement encounters.
The dismantling of USAID and significant cuts to the CDC’s global health programmes have also reduced the infrastructure available to support vaccination campaigns in partner countries, including Mexico and Guatemala — the two countries accounting for the overwhelming majority of cases.
The US Case Count and Its Context
The United States’ 1,952 confirmed cases in the first five months of 2026 represent the highest case count the country has recorded in a single year in a generation. The 2019 measles outbreak — the largest in the US since measles was declared eliminated in 2000 — recorded 1,282 cases over the entire year. The 2026 total has already exceeded that with months to spare.
The fourth overall highest state for 2026 measles infections is South Carolina, behind Utah, Texas and a fourth state — with the figures still being compiled as the outbreak continues to spread.
The geographic spread of the US outbreak — affecting multiple states in different regions — indicates that this is no longer a localised cluster situation. Community transmission is occurring across multiple states simultaneously, reflecting gaps in vaccination coverage that are widespread rather than confined to specific communities.
Why Measles Matters
Measles is often underestimated as a public health threat because it is vaccine-preventable and because many adults remember it as a common childhood illness before widespread vaccination. But measles is one of the most contagious infectious diseases known — an infected individual in a room will transmit the virus to 90% of unvaccinated people in the same space.
It kills approximately one to two children per 1,000 infected in high-income countries, and far more in settings with malnutrition and limited healthcare access. It also causes immune amnesia — a phenomenon in which infection effectively erases immunity built against other pathogens, leaving children vulnerable to a wide range of infections for months after recovery.
The 25 deaths already recorded in the 2026 Americas outbreak — in a region where a safe, effective and widely available vaccine exists — represent a preventable tragedy.
What Public Health Authorities Are Doing
PAHO has declared the Americas measles situation a public health emergency requiring regional coordination. Emergency vaccination campaigns have been launched in the most affected areas of Mexico and Guatemala. The CDC has issued guidance for healthcare providers across the US to increase suspicion and reporting of measles cases and has activated its measles emergency response protocol.
But the structural challenge — rebuilding vaccination coverage that has declined over years — cannot be solved quickly by emergency campaigns alone. The communities where coverage is lowest are often also those where trust in public health institutions is weakest, where access to healthcare is most limited, and where the competing priorities of daily economic survival make routine preventive care harder to prioritise. Rebuilding coverage in those communities requires sustained, long-term engagement — precisely the kind of investment in public health infrastructure that has been under pressure in both the US and across the Americas.
