"Every time that there's a surge in travel, we have a surge in cases in this country," said Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, at a recent White House COVID-19 task force briefing. "We know that many of our variants have emerged from international places, and we know that the travel corridor is a place where people are mixing a lot. We are really trying to restrain travel at this current period of time."