Hundreds of thousands of people, from all across the globe, are expected in Washington for Monday's presidential inauguration. Some will arrive sick -- knowingly or unknowingly -- and spread the suffering by a cough, a sneeze or by just shaking hands, sharing a cellphone or touching a door handle.
Others will arrive well and return home -- to South America or South Dakota -- bearing a miserable souvenir that takes a tour of the office, the health club, the community.
This time of year, the country's largest political party on the National Mall could also be a place where the flu, in effect, wages its own campaign.
"It's a realistic concern when you're talking about a large number of people where infectious agents can spread more readily," said Dr. Jon McCullers, an infectious disease researcher and chair of the Department of Pediatrics for the University of Tennessee Health Science Center.
All things being equal, having many people in close proximity to one another -- be it indoors or outdoors -- increases the risk of spreading the flu. And that's exactly the scenario for the inauguration, which not only brings people from all over the world together on the National Mall, but immediately before and afterward in hotels, restaurants, and on public transportation. Multiple opportunities for flu germs to spread.
"We see that in schools annually when kids are close together and in the Hajj, the pilgrimage to Mecca, there are influenza outbreaks," said Dr. Joe Bresee, a medical epidemiologist from the Centers for Disease Control and Prevention's influenza division.
Statistically, your greatest risk for influenza exposure at the inauguration might come from being near a sick child because a child's sneeze pops a much bigger wallop than an adult's does.
"An adult puts out about 10,000 virus particles per sneeze," McCullers said. "A child may sneeze out millions of virus particles per sneeze because their immune system is less developed."
Weather can have an impact on the spread of flu, too, with McCullers saying, "We know the flu transmits best in cool and dry conditions." The forecast for Monday in Washington was calling for partly cloudy skies with a high in the 30s and a very slight chance of precipitation and only light winds. Not good.
"Wind sort of carries the flu away," McCullers said, adding that ideally people would keep a distance of at least six feet to reduce the chance of transmitting the flu. That may be impossible for most people at the inauguration, but there are things that can be done there -- and elsewhere -- to avoid the flu.
-- Wash your hands regularly; don't shake hands.
-- Use hand sanitizer when soap and water are not available.
-- Practice proper cough and sneeze etiquette to prevent the spread of germs.
-- Avoid touching your eyes, nose or mouth.
-- Clean and disinfect frequently touched surfaces.
Sgt. Paul Brooks, of the U.S. Park Police said he was unaware of any plan to have hand-washing stations at the National Mall during the inauguration.
In theory, wearing gloves might seem like a good way to hedge your bet, but Bresee says, "You contaminate gloves just like you would your hands." A surgical mask might provide some benefit in a large crowd, says McCullers, "but it's not a panacea because people end up sticking their hands inside the mask."
The CDC reports 47 states having widespread flu activity. This year's vaccine, which so far has been given to about 37 percent of the American population, has been shown in a preliminary study to be 62 percent effective. Meaning, you were 62 percent less likely to get a flu virus that required you to go to your doctor.
"The flu vaccine is far from perfect," says Dr. Tom Frieden, director of the CDC. "But it's still by far the best tool we have to prevent the flu."
That said, health officials say don't make yourself sick worrying about the flu. Get your flu shot, if you haven't, and go on with your life. Attend the inauguration and other events, if that's what you want to do.
"It's the same as going to the football games that will be played this Sunday or going to church," McCullers said. "People are going to do the activities they enjoy."
And let the virus particles fall where they may.