The Pan American Health Organization (PAHO) recorded 20,521 measles cases across the Americas in 2026 and issued surveillance recommendations as the FIFA World Cup opened1. PAHO is the World Health Organization's regional office for the Americas. Mexico accounts for 10,920 of the cases and Guatemala 6,209, with the United States at 1,952 and Canada at 1,018, a regional total roughly four times the 2025 figure.
measles is the most contagious pathogen in routine circulation: a single case can infect up to 18 unprotected people, and the virus lingers airborne for up to two hours after an infected person leaves a room. A tournament hosted across the United States, Mexico and Canada moves hundreds of thousands of spectators through shared stadiums, transit hubs and host cities, mixing populations with very different vaccination coverage.
measles needs roughly 95% vaccination coverage in a population to stop circulating; below that, each imported case can seed a chain. Move large crowds from regions where coverage has slipped into venues where local pockets are also under-vaccinated, and the tournament becomes an efficient mixer for exactly that seeding. PAHO is asking health systems near venues to sharpen case detection ahead of the crowds, a preparedness signal rather than a crisis, because catching the first imported case early is what stops it becoming a cluster.
