All travelers who arrive in the United States from Ebola-stricken countries will be closely monitored for 21 days by public health officials starting Monday, the Centers for Disease Control and Prevention announced Wednesday.

Tom Frieden, director of the CDC, said that anyone arriving from the three countries – Sierra Leone, Guinea and Liberia – will be actively monitored on a daily basis and will also face new rules about where they can travel within the United States.

"These new measures I'm announcing today will give additional levels of safety so that people who develop symptoms of Ebola are isolated quickly," Frieden told reporters during a news briefing.

He added that about 70 percent of all travelers stay in six states: New York, Pennsylvania, Maryland, Virginia, New Jersey and Georgia. People will receive a kit when they arrive at the airport that explains what the symptoms are, a guide to telephone numbers, and a thermometer, Frieden said. State and local officials will maintain daily contact with travelers for the entire 21 days.

Frieden said if a traveler returning from West Africa has had no known exposure to Ebola patients, he or she will merely be monitored daily for fever.

“If, however, someone is ill, that’s a very different story,” he said. That would involve the person being isolated and, if necessary, transported by trained medical personnel.

If a person is considered “high risk” due to exposure but doesn’t appear sick, Frieden said he or she would be quarantined for the monitoring period and not allowed to travel on a commercial airline, or on other forms of public transportation such as bus or train.

“The situation will depend on the individual and their level of contact,” Frieden said.

“This is another step to protect families, communities and health care workers from Ebola,” Frieden said. “We’re tightening the process by establishing active monitoring for every traveler who returns to this country after a visit to one of the three affected countries [in West Africa]. That includes CDC employees; that includes journalists; that includes all individuals who have been there within 21 days.”

He said the intensified monitoring will take effect beginning in most states beginning on Monday. The remaining airports that receive travelers from West Africa will begin the active monitoring over the next several weeks.

“We will continue to do whatever we can to reduce risk to Americans,” he said, adding that the additional actions announced Wednesday should help lessen chances of new cases in the United States. “The risk is getting lower through these measures. But until [Ebola] is stopped at the source, we can’t make that risk zero here.”

The World Health Organization reported Wednesday that in the three West African countries there have been 4,868 deaths from Ebola and there are 9,911 confirmed, probable and suspected cases.  The numbers are as of Oct. 19 for Guinea and Sierra Leone and as of Oct. 18 for Liberia.

[This post has been updated.]