In this February 3, 2020, file photo, a security officer wearing a face mask stands on a subway train in Beijing. Health authorities are preparing for a possible pandemic as they work to contain a respiratory illness in China that's caused by a new virus. Governments are working to contain the virus by limiting travel, isolating sick people and keeping travelers returning from the affected region under quarantine to watch for symptoms. (Photo by Mark Schiefelbein/AP Photo/File)
