Increased traveling and spring break crowds are making US health experts nervous. Here’s why

More than a million passengers have traveled through US airports daily for at least 10 days in a row, according to data from the Transportation Security Administration — at a time experts say cases of a dangerous variant are climbing across the country.More than a million passengers have traveled through US airports daily for at least 10 days in a row, according to data from the Transportation Security Administration — at a time experts say cases of a dangerous variant are climbing across the country.