ATLANTA — All travelers who come into the United States from three Ebola-stricken West African nations will now be monitored for three weeks, the latest step by federal officials to keep the disease from spreading into the country.
Beginning Monday, anyone traveling from Guinea, Liberia, and Sierra Leone will have to report in with health officials daily and take their temperature twice a day.
The measure applies not only to visitors from those countries but also returning American aid workers, federal health employees, and journalists. The Centers for Disease Control and Prevention announced the new step Wednesday.
CDC director Tom Frieden said monitoring will provide an extra level of safety, on top of the temperature checks and screening that passengers already undergo before they leave West Africa and again when they arrive in the United States.
‘‘We have to keep our guard up,’’ Frieden told reporters on a conference call.
The Obama administration has resisted increasing pressure to turn away any visitors from the three countries at the center of the Ebola outbreak, especially after a Liberian visitor to Dallas came down with the disease just days after he arrived, then died.
Instead, officials began screening at five US airports and Tuesday they said all travelers from West Africa would be funneled to those airports.
The monitoring program will start in six states — New York, Pennsylvania, Maryland, Virginia, New Jersey, and Georgia — the destination for the bulk of the travelers from the outbreak region. It will later extend to other states.
Passengers will be required to provide contact information for themselves as well as a friend. They will be instructed to check for a fever twice a day and report their temperature and any symptoms to health officials daily. Frieden said states will determine how to do that, whether in person, by phone, or Skype.
If a traveler does not report in, state or local public health officials can track them down to ensure daily monitoring. How far they can go is up to those officials, CDC officials said.
They will also receive so-called CARE kits — an acronym for Check and Report Ebola. The kits include thermometer and instructions on what to do if symptoms occur. Also included is a card to present to health-care providers if they seek care.
CDC already has told its employees and other health professionals working in the outbreak zone to monitor their temperature for 21 days upon return, so Wednesday’s announcement adds another step to their ongoing fever watch. It can take several days to develop Ebola symptoms.
Earlier this year, about 150 travelers per day were from the three countries. But it appears there are far fewer now — there are no direct flights, and flights to the region have been curtailed. New York’s Kennedy airport — which handles the most traffic from the outbreak zone — has averaged 34 a day since screening began Oct. 11.
The other airports are Washington’s Dulles, Newark’s Liberty, Chicago’s O’Hare, and Atlanta’s Hartsfield-Jackson. While a few of the people screened thus far have been taken to hospitals, none had Ebola.
According to an Associated Press-GfK poll released Wednesday, Americans are worried about Ebola spreading here, and many say the government has not done enough to prevent that. The poll found a surprising 9 out of 10 people backed the tightening of screening procedures.
Some would go even further: Three-quarters think it’s definitely or probably necessary to prevent everyone traveling from places affected by Ebola from entering the United States.
On Wednesday, White House spokesman Josh Earnest said the president has followed advice from scientists that a travel ban could do more harm than good. Health officials fear travelers would just find alternate routes and enter the country unidentified, sparking harder-to-trace outbreaks.
Earnest sidestepped a question about whether the new monitoring measure is a way to avoid a travel ban.
Many health specialists agree a travel ban is a bad idea. But one faulted the CDC for being slow to begin the daily monitoring.
Monitoring can’t stop Ebola from coming in, ‘‘but we’ll have a better chance’’ to identify and isolate cases, said Dr. Richard Wenzel, a Virginia Commonwealth University scientist.
Such tracking measures might have made a difference for Thomas Eric Duncan, the Liberian who became the first person diagnosed with Ebola in the United States, Wenzel said.
Duncan was not sick and passed the screening when he left Liberia, and did not develop symptoms until days after his arrival in Dallas. He died Oct. 8.