Travelers returning to Minnesota from Liberia and two other West African nations will receive daily health checks, starting as soon as next week, for signs of Ebola until their infection risks have passed, state health officials said Wednesday.

Public health nurses or epidemiologists will call the travelers for 21 days to ask if they have symptoms and to record their temperatures, which they are supposed to take twice daily.

The surveillance program, announced Wednesday as state and federal authorities scramble to address a wave of public anxiety over Ebola, is designed to erect a new line of defense that would stop the deadly virus from spreading from West Africa, where it has infected more than 9,000 people and caused more than 4,500 deaths.

"We have to keep up our guard," said Dr. Tom Frieden, director of the U.S. Centers for Disease Control and Prevention (CDC), in a conference call Wednesday morning.

A similar strategy was used earlier this year in Nigeria, where 20 people were infected with the virus, and is credited with helping snuff out Ebola there. Public health officials believe it will prevent Ebola's spread in Minnesota, should the virus arrive, because infected people aren't contagious until they show symptoms.

"This new policy doesn't change the science," said Kris Ehresmann, director of infection control for the Minnesota Department of Health. "People who do not have symptoms are not infectious."

While federal officials said they expect daily checks to begin Monday in six other states — the destinations for 70 percent of the travelers from Liberia, Sierra Leone, and Guinea — Minnesota health officials said they are ready to launch the checks at the start of next week as well if they get the go-ahead from the CDC.

About 10 people arrive weekly from the three countries in Minnesota, which hosts one of the largest Liberian communities in the United States, so state and county public health officials could be calling as many as 30 people each day.

The check-ins will be voluntary in Minnesota, but Ehresmann said she expects most people to participate because they will want help from health officials in the event that they develop symptoms that threaten their health and pose infection risks to others. "There's definitely a motivation for people to participate," she added.

Liberians living in Minnesota might have reservations, however, because daily checks could lead to their homes being identified and families being stigmatized as Ebola risks, said Abdullah Kiatamba, a member of the Minnesota African Task Force Against Ebola.

But as long as privacy is maintained, he said, the checks will be a welcome way to protect travelers and their families and neighbors.

"When they are tracked, it helps not only [protect] the general public in the community, but it also helps the families to know that, 'my cousin, my dad, my husband is OK, and there is no threat of our family being exposed to this,' " he said.

Travelers returning from the three West African nations will be identified through screenings at customs checkpoints at airports in Chicago, New York, Newark, Atlanta, and Washington, D.C. In addition to undergoing health assessments, the travelers will provide contact information for their homes or destinations. That information will be forwarded to state health departments so they can then start checking on the travelers for 21 days, the period in which an Ebola infection would be expected to result in symptoms.

The travelers will also receive information kits with lists of symptoms and with thermometers to use twice daily.

Health officials have conducted more than 560 screenings at the five designated airports so far and have identified four travelers with symptoms suggesting a need for further evaluation. None was found to have Ebola.

"It's not rare for people to have symptoms that may be consistent" with Ebola infections, Frieden said, "especially as we head into flu season."

In Minnesota, travel to and from Liberia has slowed recently, community leaders said Wednesday. Volunteers from the Duluth Gospel Tabernacle made medical aid trips to Liberia in 2010 and 2013, but canceled plans for a trip next year and will instead conduct an aid trip to Monterrey, Mexico, said Rolf Fure, senior pastor.

The church did send 13 boxes of medical and cleaning supplies, along with financial aid, to pastors and leaders they know in Liberia, Fure said. "But Ebola will be keeping us away for a while."

Kiatamba's organization is recruiting medical volunteers to make an aid trip, and held an informational meeting last weekend to address such concerns as whether volunteers could be evacuated to the United States or whether their jobs might be jeopardized by their participation.

"People are actually scared about going back," he said, "so how do we close that?"