A Japan Airlines worker (C) wears a face mask while working inside a terminal at Los Angeles International Airport (LAX) on January 23, 2020 in Los Angeles. Mario Tama | Getty Images

U.S. travel restrictions implemented in recent days to keep a fast-moving virus that has crippled much of China from spreading across America won't work, a top epidemiologist told U.S. lawmakers Wednesday. "I have never seen instances where that has worked when we are talking about a virus at this scale," epidemiologist Jennifer Nuzzo, a senior scholar at Johns Hopkins University's Center for Health Security, testified before the House Foreign Affairs subcommittee. Respiratory viruses like the one that's sickened more than 24,300 across the globe and killed at least 490 in China "just move quickly," she said. "They are hard to spot because they look like many other diseases. It's very hard to interrupt them at borders. You would need to have complete surveillance in order to do that. And we simply don't have that," she said.

In China, physicians are looking for sick people, while other countries are looking for people from China. Somewhere in between, infected people are going to be missed, she said. "For that, and other reasons, I do not believe we're going to be able to keep the virus out of our border," she said, adding that a bigger concern is that the travel restrictions and mandatory quarantines are diverting resources away from fighting the virus. One public health department has 31 health-care workers monitoring two quarantined patients 24 hours a day, she said. "As this epidemic grows, that's not likely to scale," she said. Other witnesses included Jennifer Bouey, senior policy researcher at the Rand Corporation, and Ron Klain, former White House Ebola response coordinator. Rep. Ami Bera, D-Calif., chairman of the House Foreign Affairs Subcommittee on Asia, the Pacific, and Nonproliferation, announced the hearing last week. "While the threat of the coronavirus is relatively low in the United States at this time, we must be vigilant and prepared," Bera said in a statement. "I look forward to hearing from our expert witnesses on ways in which we can plan and respond to this virus. Congress needs to ensure the administration has the tools it needs to respond to and limit the outbreak."