WASHINGTON (AP) — Significantly expanding their vigilance, federal health officials said Wednesday that they would begin monitoring all travelers — even Americans — who come to the U.S. from Ebola-stricken West African nations for 21 days.

Dr. Tom Frieden, director of the Centers for Disease Control and Prevention, said the expanded screening would begin Monday in six states — New York, Pennsylvania, Maryland, Virginia, New York and Georgia.

He said the new system would further protect Americans. "The bottom line is that we have to keep our guard against Ebola," he said.

Travelers from those countries will be given information cards and a thermometer and be required to make daily check-ins with state or local health officials to report their status. He said the check-ins could be in person, by telephone, Skype or Facetime or through employers — CDC was consulting with the state and local officials to help them work that out.

The travelers would be required to report any travel plans.

Frieden said if they don't cooperate, they would be immediately called in.