The upcoming 2026 FIFA World Cup, starting on June 11, 2026, will see millions of fans converging in 16 cities across the United States, Canada, and Mexico, creating a conducive environment for infectious disease transmission. Health experts are particularly concerned about respiratory infections like measles, which has seen a significant rise in cases, with 2,030 confirmed in the U.S. by June 2026. The flu season has also reached a 30-year high, and COVID-19 continues to pose risks. Mosquito-borne diseases, especially dengue, have increased dramatically, with nearly 3,800 cases reported in 2024. Additionally, sexually transmitted infections, including mpox and syphilis, are under scrutiny due to the likelihood of casual encounters among international travelers. Public health authorities are ramping up monitoring efforts, but experts express concerns about the resilience of U.S. public health systems, which have faced budget cuts. Fans are encouraged to ensure vaccinations are current, practice safe sex, and take precautions against mosquito bites to mitigate these health risks.