(CNN) -- Both Americans who were treated for the Ebola virus have been discharged from a hospital.
"Today is a miraculous day," Dr. Kent Brantly said at a Thursday news conference in Atlanta with Emory University Hospital staff members. "I am thrilled to be alive, to be well and to be reunited with my family." The hospital had announced that he was being discharged Thursday.
The other patient, Nancy Writebol, was released Tuesday and is choosing not to make public comments, the hospital said.
Emory's staff is confident that their discharges pose "no public health threat," said Dr. Bruce Ribner, director of Emory's Infectious Disease Unit, adding that Writebol requested her discharge not be publicly announced at the time.
As she walked out of her isolation room, Writebol said, "To God be the glory," Brantly said at the news conference.
"We are tremendously pleased with Dr. Brantly and Mrs. Writebol's recovery," Ribner said.
"What we learned in caring for them will help advance the world's understanding of how to treat Ebola infections and help, hopefully, to improve survival" in other parts of the world, Ribner said at the news conference.
"There may be some recovery time because this is a fairly devastating disease," but in general, patients without organ damage are expected to "make a complete recovery," he said.
There is strong epidemiological evidence that after an Ebola patient survives the disease, the survivor becomes immune to that particular strain of Ebola, Ribner told reporters Thursday.
Both patients were evacuated from Liberia this month, in a plane specially equipped with an isolation tent, and accompanied by medical staff outfitted in head-to-foot protective clothing. The plane was able to take only one patient at a time and made two trips. The patients were taken to an isolation unit at Emory.
Asked about the role that an experimental serum played in the recoveries, Ribner said doctors "do not know whether it helped them, whether it made no difference," or whether it might have delayed their recovery.
Ribner said he also did not know whether Brantly was helped by a blood transfusion he received from a young Ebola survivor in Liberia.
Joy and relief
Brantly was in Liberia for faith-based charity Samaritan's Purse, and its president, Franklin Graham expressed joy over the doctor's release.
"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," he said.
Writebol's husband, David, who was with her in Africa, visited her at Emory on Sunday, he said in a statement. She is recovering, he said.
He stood outside the isolation room, as they looked at each other through the glass.
"We both placed our hands on opposite sides of the glass, moved with tears to look at each other again," he said.
For Brantly to leave isolation, two blood tests done in a two-day period had to come back negative.
The Ebola virus spreads via direct contact with bodily fluids, like blood, sweat and feces. Brantly's will no longer be infectious.
There is a slight possibility that the virus could linger for up to three months in his semen, according to the World Health Organization.
The virus has no known cure, and left untreated, infections can be deadly in up to 90% of cases. Nearly half the patients receiving medical care in the current outbreak in Liberia, Sierra Leone, Nigeria and Guinea are surviving.
Treatment consists of giving fluids, monitoring vital signs and responding to acute medical crises. Symptoms include fever, aches, diarrhea and bleeding.
Brantly and Writebol also received an experimental drug called ZMapp, which was also given to three health care workers in Liberia, who appear to be recovering.
Fears of U.S. outbreak
Brantly and Writebol were the first known people infected with Ebola to enter the United States.
Their arrival triggered a surge of angst on social media from people afraid the patients could spread the virus.
But experts have said that additional infected people could cross U.S. borders by happenstance, given the proliferation of international air travel and the enormity of the current outbreak.
But they have dismissed the notion that infection could spread significantly in the country, thus turning into an outbreak.
More than 1,350 people have died in the West African Ebola outbreak since the first cases drew attention in March, the WHO said Wednesday.
Aid workers are fighting an uphill battle to stop the disease as it continues to spread. Financial and human resources have been stretched.
An emergency research "all call" was issued Thursday by medical charity Wellcome Trust and United Kingdom's Department for International Development to find a drug to stop the outbreak.
They are making $10.8 million available to fund research. Wellcome Trust is committing another $66.5 million to the development of health research scientists in Africa, who are studying many deadly diseases there.
Canada's public health agency had 800 to 1,000 doses of a vaccine known as VSV-EBOV delivered to health officials in Liberia last week.
Mapp Biopharmaceuticals, which produces ZMapp, said it has sent its entire stock of the experimental drug overseas to fight the outbreak.
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