(CNN) — Three more American aid worker who were exposed to Ebola in Sierra Leone are due to arrive back in the United States on Monday for monitoring. None of them are sick or known to be infected with the disease.
Eight of their colleagues have already been flown back to the United States where health authorities are watching them closely for signs of the disease, according to the Centers for Disease Control and Prevention.
The returning workers are clinicians for Partners in Health, a Boston-based aid group. They are showing no symptoms of Ebola, but all had contact with a colleague who’s been diagnosed with the disease and is being treated at the National Institutes of Health in Bethesda, Maryland.
While in West Africa, the workers “came to the aid of their ailing colleague,” according to a Partners in Health statement.
As the CDC investigates who else might have had contact with the Ebola patient, more workers might be flown back to the United States, according to Tom Skinner, a spokesman for the CDC.
The workers are being housed near hospitals that specialize in treating Ebola patients, and if they show signs of the disease, they’ll be admitted as patients.
Coming to Nebraska, Georgia, Maryland
Four of the clinicians arrived Saturday to housing on the campus of the University of Nebraska Medical Center in Omaha, according to spokesman Taylor Wilson. The workers have voluntarily agreed not to leave their housing.
“They will be monitored so they’ll stay there,” Wilson said.
Another aid worker was flown to Atlanta over the weekend and is being housed near Emory University Hospital, and three more workers are scheduled to arrive in Atlanta on Monday, according to Nancy Nydam, spokeswoman for the Georgia Department of Public Health.
As in Nebraska, the workers in Georgia must stay in their housing for 21 days after the date of their exposure to Ebola.
“Twice a day, we’ll have visual monitoring either face to face or we’ll Skype with them, or do FaceTime,” Nydam said. “And if it’s Skype or FaceTIme, they’ll have to be in a place where we can clearly identify that they are where they’re supposed to be.”
Three more exposed workers arrived Saturday at the National Institute of Health in Maryland.
These workers “will remain restricted from public places” and have “limited movement, including no mass transportation,” according to a statement from Christopher Garrett, a spokesman for the Maryland Department of Health.
The heath care worker with Ebola was in serious condition Friday, the NIH said. Details about the patient’s identity weren’t released.
The patient is the second with Ebola admitted to the NIH hospital.
A deadly and stubborn epidemic
Nina Pham, a nurse at Texas Health Presbyterian Hospital Dallas, was admitted to NIH in October after she contracted the disease while treating Liberian national Thomas Eric Duncan. Pham recovered and was released free of disease. Duncan died.
Emory, the NIH and Nebraska are three of only four hospitals in the United States that have biocontainment units to deal with a highly infectious disease such as Ebola.
More than 10,000 people have died in a West African epidemic of Ebola that dates back to December 2013, according to the World Health Organization. Almost all of the deaths have been in Guinea, Liberia and Sierra Leone.
Ebola is spread by direct contact with the bodily fluids of an infected person.
CNN’s Carma Hassan, Joe Sutton and Eliott C. McLaughlin contributed to this report.