Stepping up their vigilance against Ebola, federal authorities said Wednesday that everyone traveling into the U.S. from Ebola-stricken nations will be monitored for symptoms for 21 days. That includes returning American aid workers, federal health employees and journalists, as well as West African travelers.

The program will start Monday in six states that represent 70 percent of people arriving from Liberia, Sierra Leone and Guinea, said the Centers for Disease Control and Prevention. CDC Director Tom Frieden said monitoring would extend to other states in coming days and reach “every person coming back to the country for the 21 days they are at risk for Ebola.”

He said it would continue until the outbreak in West Africa is controlled.