As U.S. officials declared the new coronavirus outbreak a public health emergency — imposing measures such as temporary quarantines for people possibly exposed to the virus, and barring entry of foreign nationals who have recently visited China — some experts questioned whether the approach would be effective. A steep rise in the number of cases in recent days, as well as lingering unknowns about the new virus, called 2019 novel coronavirus, or 2019-nCoV, including its severity and transmissibility, prompted officials to take the actions, said Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases in Bethesda, Md. at a White House news briefing announcing the measures on January 31. “It was not clear whether an asymptomatic person could transmit it while they were asymptomatic. Now we know from a recent report from Germany that is absolutely the case,” he said. Two coworkers at a car parts supplier in Germany passed the virus to others before d