With one million people expected to attend Super Bowl-related events in Minneapolis, Minnesota, this weekend, health officials are worried that the deadly strain of influenza that has been widespread throughout the United States this winter will spread even more quickly.

CBS News reported that “fans from the teams’ home cities, Boston and Philadelphia, can carry the virus back home. Researchers have found an 18 percent increased risk of flu-related death for people over 64 in those cities after the Super Bowl.

The news outlet continued: “Epidemiologist Mike Osterholm says fans are upping their odds of contracting the flu if they go to the game.”

“‘Think of influenza almost like a lottery,’ he said. ‘If a normal day you’d only come in contact with 10 people that’s one chance, 100 or a thousand you just upped your chances that much more.’”

About 65,000 fans have tickets for Super Bowl LII, which will take place in the U.S. Bank Stadium in downtown Minneapolis between the New England Patriots and the Philadelphia Eagles. But fans are not the only ones at risk—a Patriots player was hospitalized this week for symptoms of flu.

Minnesota is currently classified by the Centers for Disease Control and Prevention as experiencing a “widespread” flu outbreak. The number of hospitalizations remains high in now the fourth week the virus has been widespread in the state.