June 8 (UPI) -- When the 2026 FIFA World Cup begins on June 11, 2026, matches will be played across 16 cities in the United States, Canada and Mexico. Millions of fans will arrive through multiple airports and will pack into stadiums, airports, hotels, bars and public transit systems over five weeks. That makes the World Cup not just a sporting event but a weekslong experiment in global mixing that creates a perfect environment for infectious diseases to spread. Events of this scale rarely