Five U.S. cities have begun testing people with flu-like symptoms to see if they might instead have the new coronavirus that originated in China, a sign that officials think cases of the virus may be seeping into the country despite screening at airports.

Health and Human Services Secretary Alex Azar announced the initiative during a Senate panel on Thursday, where he was discussing the president’s budget proposal. Elaborating on NPR Friday, Azar said the Centers for Disease Control and Prevention was working with health departments in Seattle, San Francisco, Chicago, New York, and Los Angeles to test people for coronavirus who show up to doctor’s offices and hospitals with flu symptoms.