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 cause major outbreaks, but they do create opportunities for outbreaks and for health systems to be tested.

The possibilities range from the dramatic but unlikely (an imported Ebola case) to the much more probable (flu and measles spreading through crowded venues) and the largely overlooked (spikes in sexually transmitted infections and mosquito-borne diseases gaining footholds in new areas).

As an infectious diseases physician studying how outbreaks affect peoples’ health, and an avid soccer fan – I root for the Colombian team – I have been watching closely as public health experts prepare for the event.

Here are some of the infectious disease threats they are monitoring as the world’s largest sporting event kicks off:

Ebola – scary but unlikely

In May 2026, the World Health Organization declared a global health emergency over an Ebola outbreak in the Democratic Republic of Congo and Uganda caused by a rare strain called Bundibugyo, which kills roughly 1 in 3 people it infects.

No approved vaccines, rapid diagnostic tests or treatments exist for this strain. And the global response has been complicated by deep cuts to international health aid and the U.S. withdrawal from the World........

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