A measles outbreak, heat events and food-borne illnesses are among the potential health hazards at the FIFA World Cup that public health officials in Toronto, Vancouver and cities in the U.S. and Mexico aim to mitigate by sifting through wastewater and social media.

The 39-day event kicked off on Thursday in Mexico, and matches will be played on Friday in Toronto and Saturday in Vancouver.

More than 6.5 million soccer fans from around the world are expected to attend games in the three host nations — a scale of travel that boosts the risk of rapid disease spread just as outbreaks of measles, Ebola and the Andes strain of hantavirus, which was recently linked to an outbreak on a cruise ship, have hit globally.