coronavirus, and nbc's antonia hylton, yamiche alcindor, the moderator of with the washington week" and dr. vin gupta, pulmonologist. antonia, the new covid testing rules for international travel went into effect today. what are you seeing at one of the country's busiest airports? >> reporter: that's right. as of 12:01 a.m. this morning, these new restrictions and test requirements got in place. if you're a traveler who's already abroad or you are planning to travel out of the country anytime soon, in order to come back and enter the united states, you're going to have a one-day window to get a negative covid test back. and that applies to basically everyone, if you're over 2 years old, if you are vaccinated or unvaccinated and it doesn't matter what country you are coming back from. and that one-day window is key. people have been operating with a 72-hour window up until now, and so travelers really need to