Transcript for Flu Outbreak Update, Latest on Nationwide Spread
In the nation's capital, the final preparations are under way for the inauguration. As many as 800,000 people expected to attend. Even as the cdc has issued a new warning about the flu and being careful of crowds. Today a scientist has said the flu has spread to 48 states. Though we seem to be halfway through the crisis, about another six weeks to go, we wondered what about the crush of a crowd in washington? How many of those people could come home from the inauguration sick? Here's abc's lisa stark. Reporter: They're welcoming guessing with champagne and hand sanitizerer. The hotel is worried about the flu. Reporter: Some 600,000 people are expected to jam the nation's capital, flying in on planes, packing hotels, rubbing elbows at the balls. Over the course of a flu season, as many as 20% of americans get sick. Do the math. That could mean thousands of potentially infected visitors. A person with the flu can spread the virus to those around them. If I'm by myself, no worries. But on monday, this spot near the u.S. Capitol will look like it did four years ago. Packed with people who come from around the country. There's a dangerous zone. If someone neezs those droplets can spread six feet. In a packed crowd, more than a dozen people could be in harm's way. The risk is the greatest from the smallest among us. A child's sneeze can spread millions of virus particles, ten times more than an adult because adults have a more developed immune system. Doctors say take common sense precautions, get the flu shot, wash your hands, and just as important -- if somebody has the flu, they're best off staying at home. They might be sick and not feel well. The best seat in the house will be on their couch. Reporter: You'll feel better and so will everyone else. Lisa stark, abc news, washington.
This transcript has been automatically generated and may not be 100% accurate.