The Super Bowl party is full of dangers.

There’s getting to the party in the first place—drunk-driving accidents increase on game day—and then there’s the stress of watching it. There are calorie-laden snacks galore. There’s beer, which means there are aluminum tabs on beer cans, which are apparently a common choking hazard during Super Bowl Sunday. There’s that co-worker who asked you about your plans for the game, and then you felt like you had to ask him about his, and he said he didn’t have any, and then it got awkward, and, well, now here’s here, and you have to talk to him.

Then there’s the flu virus.

In a new paper, researchers from Tulane University and the College of William and Mary reported that sending a team to the Super Bowl is linked to a nastier local flu season. Combing through county-level statistics from 1974-2009, the researchers found that places with Super Bowl teams saw 18 percent spike in flu-related deaths among people over the age of 65, who are generally the most vulnerable to the disease.

There are a few reasons why the game might lead to more cases of the flu, said Charles Stoecker, a health economist at Tulane and a co-author of the paper. The first and most obvious is that the Super Bowl, like any other major viewing event, puts a lot of people together to eat and drink and breathe in the same room, making it easier for the flu to spread from person to person. (The virus can travel up to six feet in a sneeze. Plus, double-dipping.) The second, he said, is that the game also changes travel patterns, again leading to increased contact with a higher number of people.

And the third is that Super Bowl Sunday is also lucrative for bars and restaurants: “You want to be out, you want to be seen, you want to celebrate your team’s success in a very public way,” Stoecker said, which can affect customers and employees alike. “Let’s say that a city sees a spike in bar attendance as people celebrate the victory,” he said. “There are more jobs created in tourism and entertainment, and it could be that those workers are facilitating the spread … You’re pulling in workers from a sector where they don’t have a whole lot of mixing contact, and you’re putting them in the amusement and recreation sector, where they do.”

The phenomenon isn’t unique to the Super Bowl. Past studies have found spikes in flu transmission during the 2002 Winter Olympics in Salt Late City, the 2006 World Cup in Germany, the annual pilgrimage to Mecca,  and music festivals (which, in the interest of spoiling all the fun, were also linked to increased rates of transmission for a whole host of other things, including hepatitis A, measles, and E. coli infections). Stoecker and his colleagues found that the flu effect wasn’t as pronounced for the Super Bowl host city, though, possibly because, as they wrote, “host cities may see an influx of income, raising health and health behavior; local mixing within hosting cities may not increase as a consequence of the Super Bowl game; or locals may actually decrease mixing in response to increased travelers (avoiding traffic, busy restaurants, etc.).”

The best way to mitigate the Super Bowl effect, Stoecker said, is for residents of Seattle and Boston to get vaccinated—but “for this weekend, it’s kind of too late for that to happen. So wash your hands and be careful around the dip.”

And as for his own game day plans: “I went to school in Boston for six years, and old loyalties die hard,” he said. “I’ll of course be attending a party. And washing my hands.”