Huge crowds and low vaccination rates raise measles alarms as Pope Leo XIV visits South America

While millions of Catholics gather to catch a glimpse of Pope Leo XIV in South America, health authorities are watching for a different kind of visitor: measles.Cases are already surging in the region this year and mass gatherings provide an opportunity for one of the world's most contagious viruses to spread further.The Pan American Health Organization, or PAHO, and officials in Uruguay, Argentina and Peru have been preparing for potential problems to different degrees for months, including mounting vaccination campaigns and increasing surveillance to try to limit spread.

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Uruguay, where thousands of people attended a prayer vigil and a Mass celebrated by Leo, implemented a nationwide intensified surveillance monitoring period until Nov. 29, three weeks after Leo’s departure from the country, according to Nataly Rodriguez, director of epidemiology at Uruguay’s health ministry. Uruguay has also taken steps to boost its vaccination rate to among the highest in the region. “As a preventive