When the 2026 FIFA World Cup kicks off on June 11, measles will pose a far greater threat to the millions of fans packing stadiums, airports and bars than the high-profile Ebola outbreak in central Africa, public health officials say. The tournament, the first to be co-hosted by three nations and the first to feature 48 teams, will run for five weeks across 16 cities in the United States, Canada and Mexico — a weeks-long experiment in global mixing that creates a perfect environment for infectious diseases to spread.
Of all the threats on the radar, respiratory infections are the likeliest to cause trouble, with measles standing out as the most contagious. As of June 4, the U.S. Centers for Disease Control and Prevention has confirmed 2,030 measles cases in the United States in 2026, approaching the total for all of 2025 (2,288 cases and 48 outbreaks) and far exceeding the 16 outbreaks reported in 2024. The CDC notes that roughly 92% of cases this year have been in unvaccinated individuals or those with unknown vaccination status, a pattern it attributes to declining vaccination rates and disruptions to routine immunisation programmes.
Measles spreads through coughing, sneezing and even breathing in crowded spaces, making stadiums, airport terminals, hotels and public transport ideal transmission zones. The CDC points to a single infectious traveller passing through Denver International Airport in 2025 who triggered an outbreak of at least 10 cases. An infected fan in the stands, at an airport or in a bar could easily cause a similar chain of infections. “Measles is one of the most contagious infectious diseases on the planet,” the original analysis notes, and the surge across North America — also affecting Canada and Mexico — means the risk to World Cup attendees is significantly elevated.
Influenza adds another layer of concern. The 2025–2026 flu season reached a 30-year high, with the CDC reporting six additional paediatric influenza-related deaths during that period, bringing the total to 172. Approximately 85% of those deaths occurred in unvaccinated children. COVID-19 continues to cause an estimated 290,000 to 450,000 hospitalisations per year in the U.S., and mass gatherings amplify the risk of transmission. In the background, avian influenza H5N1 — the bird flu circulating in dairy cows and poultry — has caused 71 human infections in the U.S. since 2024, with two deaths. The CDC considers the risk to the general public low because no person-to-person spread has been detected, but scientists are watching closely for mutations that could change that.
Ebola — scary but unlikely
While the Ebola outbreak in the Democratic Republic of Congo and Uganda has grabbed headlines, the risk of it reaching a World Cup stadium is very low. The World Health Organization declared a public health emergency of international concern on May 16, 2026, after the Bundibugyo strain of the virus — which kills roughly one in three people it infects — emerged in the region. As of June 10, the DRC had reported 515 confirmed cases and 91 deaths (a case fatality rate of 17.7%), while Uganda had 19 confirmed cases including two deaths. 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 WHO.
Ebola spreads only through direct contact with bodily fluids such as blood or saliva, not through the air, and infected people are not contagious until they show symptoms. The U.S. has banned entry for non-U.S. citizens and green card holders who have been in the affected countries — including South Sudan — within the past 21 days, and is screening all passengers travelling from those areas. Affected air passengers are being rerouted to specific U.S. airports for enhanced health screening. Mexico and Canada have also implemented travel restrictions. The CDC assesses the overall risk to the U.S. public and travellers as low.
Mosquito-borne risks in southern host cities
Matches in southern U.S. and Mexican host cities during peak summer mosquito season add another layer of risk. Dengue set a U.S. record in 2024, with 3,798 cases — a 359% jump over the 2010–2023 average. The CDC says 97.2% of those cases were travel-associated, but locally acquired cases have cropped up, mainly in Los Angeles. Yellow fever, absent from the U.S., remains a threat to fans travelling from parts of Sub-Saharan Africa and South America, where the disease is endemic. A 2024 outbreak in South America outside the Amazonian jungle hinted at possible urban spread. Oropouche virus, a once-obscure mosquito-borne illness, exploded across Latin America in 2024 in the largest epidemic ever recorded, with over 8,000 confirmed cases in Brazil alone. While infection is usually mild, it can cause brain inflammation, bleeding disorders and harm to a developing fetus. No vaccines or treatments exist. Travelers carrying these infections may need medical care, but familiarity among U.S. physicians tends to be low, and there is a small risk that illnesses could spread locally through mosquito bites.
Sexually transmitted infections under the radar
One category receiving less media attention is sexually transmitted infections. About one in five international travellers engages in casual sex, according to one study, and nearly half of those encounters are unprotected. Mpox, a viral infection that spreads through close physical contact, continues to circulate in the U.S. and is a particular concern at large public events. Syphilis is also seeing a global resurgence, with cases tripling in the U.S. since 2010 to levels not seen since the 1950s, and rising rates of congenital syphilis reported in the U.S., UK, Canada and Japan, driven by declining condom use and increased casual sex facilitated by digital platforms.
Public health preparations and concerns
Public health authorities across the U.S., Canada and Mexico have scaled up monitoring. In the U.S., a coalition of academic institutions, companies, nonprofits and public health organisations led by Georgetown University and MedStar Health — called the Health Security Operations Center — will be tracking disease transmission throughout the tournament. But some experts have raised concerns about U.S. resilience to public health threats at the World Cup, citing significant cuts to public health infrastructure since 2025, including to the CDC. Fans can take several steps to protect themselves: ensure routine vaccinations — especially measles, flu and COVID-19 — are up to date; practice safe sex; use mosquito repellent; and stay home or wear a mask if they feel sick.