This weekend will be big for movie buffs, football fans and Barack Obama. But as Americans flock to the Sundance Film Festival, the NFL playoffs and the Presidential Inauguration, the weekend could also be big for the flu.
About 35,000 Americans have been sickened by an early and nasty wave of influenza, according to the U.S. Centers for Disease Control and Prevention. And while the outbreak appears to be abating, flu activity is still widespread.
"Our biggest concern is people coming in asymptomatic but carrying the virus," said Rob Allen, chief executive officer of Park City Hospital in Park City, Utah, the home of Sundance.
Utah is one of 33 states reporting high levels of influenza activity. And Park City, home to roughly 40,000 people, will more than double its population this weekend as actors, director, producers and fans fill its hotels, restaurants and theaters.
"We have 50,000 people coming in, potentially bringing with them flu from their areas," said Allen, who partnered with local businesses to distribute hand sanitizer as visitors arrive. "If they practice good hand hygiene, hopefully they won't spread it so we can keep it isolated."
The flu virus spreads through microscopic respiratory droplets that travel six feet in a cough or a sneeze and survive on skin and other surfaces.
"And influenza can be spread by someone who's not yet sick," said Dr. William Schaffner, chair of preventive medicine at Vanderbilt University Medical Center in Nashville, Tenn. "They'll become sick tomorrow, but today they're emitting the virus as they exhale."
The best protection against the flu, according to the CDC, is the flu shot. This year's vaccine guards against three widespread strains of the virus and is 62 percent effective.
"We recognize that the vaccine is not 100 percent effective, but it's the foundation on which all other protection is built," said Schaffer.
Frequent hand washing and the use of hand sanitizer can also guard against the virus. The Georgia Dome – home of the Atlanta Falcons and Sunday's National Football Conference championship football game – has hand sanitizer pumps at every entry gate.
"That's standard policy for us," said Jason Kirksey, a spokesman for the 70,000-seat stadium. "With any event we have here, the safety and security of our fans is our number one priority, and that includes protection from any kind of airborne disease."
But football fans should still fight the urge to high-five and hug, according to Schaffner.
"School children are now taught that during an influenza outbreak, handshakes are out," he said, describing how flu-fearing students are bumping elbows in lieu of high-fives. "But at exciting and emotional events, it's hard to resist. So get vaccinated and try not to hug someone who's coughing or sneezing."
Sunday's Presidential Inauguration is expected to draw 800,000 people to Washington, D.C., where the U.S. Department of Health and Human Services will man medical stations along the National Mall.
"Our advice for the inauguration is the same advice for a day-to-day basis," said HHS spokeswoman Elleen Kane. "Make sure you get the flu shot; if you cough or sneeze, do it into your elbow; wash your hands frequently and keep them away from your nose and mouth; and if you feel sick, stay home."
"It's pretty hard to protect yourself from the flu when you are in a crowd," said ABC News' chief health and medical editor Dr. Richard Besser. "Sure, you can use hand sanitizer to clean your hands. But when the person next to you lets go with a big sneeze or a cough, you are sunk."
And it's not just the crowded events, according to Schaffner. "It's the travel to and from the events," he said, describing how packed airplanes and busy airports can teem with germs. "There's only so much you can do when you're in 13C and someone's sneezing in 13B. It's an unlucky row."
So while the weekend will be big, it's not worth risking the health of those around you, according to Besser.
"If you have a fever or you are just getting over the flu, stay home," he said. "I know it's hard to do when it's an event you've really been waiting for, but it's the right thing to do."