ATLANTA — At least one of the two American aid workers who were infected with the deadly Ebola virus in Africa has recovered and was to be discharged Thursday from an Atlanta hospital, a spokeswoman for the aid group he was working for said.

Alison Geist, a spokeswoman for Samaritan's Purse, told The Associated Press she did not know the exact time Dr. Kent Brantly would be released but confirmed it would happen Thursday.

Emory University Hospital planned to hold a news conference Thursday morning to discuss both patients' discharge. Brantly will speak but won't take questions, according to a news release. Emory spokeswoman Holly Korschun did not give further details on either patient, citing privacy concerns.

Franklin Graham, president of North Carolina-based Samaritan's Purse, said in a statement that the group was celebrating Brantly's recovery. He has been in the hospital's isolation unit for nearly three weeks.

"Today I join all of our Samaritan's Purse team around the world in giving thanks to God as we celebrate Dr. Kent Brantly's recovery from Ebola and release from the hospital," Graham's statement said.

Brantly, 33, was flown out of the west African nation of Liberia on Aug. 2, and Nancy Writebol, 59, followed Aug. 5. The two were infected while working at a missionary clinic outside Liberia's capital.

Writebol was working for North Carolina-based aid group SIM. The organization plans to release a statement Thursday, spokesman Palmer Holt said in an email but gave no further details.

Brantly and Writebol received an experimental treatment called Zmapp, but it's not know whether the drug helped or whether they improved on their own, as has happened to others who have survived the disease. The treatment is so novel that it hasn't been tested in people.

The limited supply of Zmapp also was tried in a Spanish missionary priest, who died, and three Liberian health care workers, who are said to be improving.

The Ebola outbreak has killed 1,350 people and counting across West Africa. There is no proven treatment or vaccine. Patients are given basic supportive care to keep them hydrated, maintain their blood pressure and treat any complicating infections. Ebola is spread only through direct contact with the bodily fluids of sick people experiencing symptoms.

On Thursday in the Liberian capital of Monrovia, calm set in one day after residents in a slum that was sealed off in an effort to contain the outbreak clashed with riot police and soldiers. World Health Organization officials were visiting two hospitals that are treating Ebola patients and struggling to keep up with the influx of patients.

The death toll is rising most quickly in Liberia, which now accounts for at least 576 of the fatalities, the WHO said. At least 2,473 people have been sickened across West Africa — more than the caseloads of all the previous two-dozen Ebola outbreaks combined.