The 2026 FIFA World Cup kicks off on June 11, with matches taking place across 16 cities in the United States, Canada, and Mexico. Millions of fans will arrive through dozens of airports and spend five weeks filling stadiums, hotels, bars, airports, and public transportation systems.

This makes the World Cup not only the world’s biggest sporting event but also a massive experiment in global human mixing, creating ideal conditions for infectious diseases to spread. While events of this scale rarely trigger major epidemics, they can significantly increase the risk of outbreaks and put public health systems to the test.

The range of potential threats is broad — from unlikely but alarming scenarios such as imported Ebola cases to the far more probable spread of influenza and measles in crowded venues. Less visible risks include increases in sexually transmitted infections and the introduction of mosquito-borne diseases into new areas.

As an infectious disease specialist who studies how outbreaks affect public health, and as a devoted soccer fan who supports Colombia’s national team, I have been closely following preparations by public health authorities ahead of the tournament.

Below are the key infectious disease threats experts are monitoring as the world’s largest football event approaches.

Ebola: A Frightening but Unlikely Threat

In May 2026, the World Health Organization declared a public health emergency in response to an Ebola outbreak in the Democratic Republic of the Congo and Uganda. The outbreak is being driven by the rare Bundibugyo strain, which kills roughly one in three infected individuals.

There are currently no approved vaccines, rapid diagnostic tests, or specific treatments for this strain. The response has also been complicated by reductions in international health funding and the United States’ withdrawal from the WHO.

If a case is detected, rapid identification and isolation of the patient will be essential to prevent further transmission.

Nevertheless, the likelihood of Ebola reaching a World Cup stadium remains extremely low. The virus spreads only through direct contact with bodily fluids such as blood, saliva, and other secretions. Infected individuals do not become contagious until symptoms appear.

The United States has barred entry to foreign nationals and green card holders who have visited affected countries within the previous 21 days and has strengthened screening measures for travelers arriving from those regions. Similar restrictions are in place in Canada and Mexico.

Measles, Influenza, and COVID-19: The More Likely Threats

Respiratory infections transmitted through coughing, sneezing, and close contact in crowded environments pose the greatest risk to fans attending the tournament.

Measles is of particular concern, with cases rising rapidly in the United States, Canada, and Mexico. According to the U.S. Centers for Disease Control and Prevention (CDC), 2,030 measles cases had been confirmed in the United States as of June 4, 2026 — nearly matching the total number recorded throughout 2025 and far exceeding levels seen in previous years.

Measles is one of the most contagious infectious diseases in the world. In 2025, a single infected traveler passing through Denver International Airport triggered an outbreak involving at least ten cases. Likewise, one infected fan at a stadium, airport, or bar could easily spark a new outbreak.

Health officials are also concerned about the severe 2025–2026 influenza season, the worst in three decades. COVID-19 continues to pose a substantial burden as well, causing an estimated 290,000 to 450,000 hospitalizations annually in the United States. Large gatherings can significantly increase transmission risks for both viruses.

Scientists are also closely monitoring avian influenza H5N1, which continues to circulate among dairy cattle and poultry. Since 2024, 70 human infections have been reported in the United States. Although no person-to-person transmission has been documented, experts remain alert for mutations that could alter the situation.

Mosquito-Borne Diseases

Mosquito-transmitted illnesses represent another concern, particularly in southern U.S. states and Mexican host cities where matches will be held during peak mosquito season.

Dengue fever, which causes high fever, severe muscle and joint pain, and occasionally life-threatening complications, reached record levels in the United States in 2024. Nearly 3,800 cases were reported, representing a 359% increase over the average of the previous 14 years.

Most infections were linked to travel in the Caribbean and Central America, although locally acquired cases have also been reported, particularly in Los Angeles.

Experts are also concerned about the importation of other diseases. Yellow fever remains endemic in parts of sub-Saharan Africa and South America. An outbreak in South America during 2024 outside the virus’s traditional transmission zones suggested that it could spread into densely populated urban areas.

Another emerging threat is Oropouche virus, which caused the largest outbreak ever recorded in Latin America in 2024. More than 8,000 cases were confirmed in Brazil alone. Although the disease is usually mild, it can lead to serious complications, including brain inflammation, bleeding disorders, and pregnancy-related risks. No vaccine or specific treatment is currently available.

Sexually Transmitted Infections

The risk of sexually transmitted infections (STIs) has received less media attention but remains a concern.

Research suggests that approximately one in five international travelers engages in casual sexual activity while abroad, and nearly half of those encounters occur without protection.

Health experts are particularly concerned about mpox, which continues to circulate in the United States and may spread more easily during large public events. Syphilis rates are also rising in many countries around the world.

Public Health Preparations

Health authorities in the United States, Canada, and Mexico have intensified disease surveillance efforts ahead of the tournament. In the United States, a dedicated Health Security Operations Center established with the participation of Georgetown University and MedStar Health will monitor potential public health threats throughout the event.

Experts recommend that fans ensure their vaccinations are up to date, particularly for measles, influenza, and COVID-19. They also advise practicing safe sex, using mosquito repellents, and staying home or wearing a mask if symptoms of illness develop.

According to public health specialists, prevention and the rapid detection of infectious diseases will be essential to ensuring that the 2026 FIFA World Cup remains safe for millions of fans from around the globe.