ATLANTA (CNN) -- An American doctor infected with Ebola in Liberia "seems to be improving," according to the director of the Centers for Disease Control and Prevention.
"It's encouraging that he seems to be improving," Thomas Frieden said of Dr. Kent Brantly on CBS' "Face the Nation" on Sunday. "That is really important, and we are hoping he will continue to improve."
The Christian charity that employs Brantly confirmed Sunday that the 33-year-old doctor received a dose of an experimental serum before leaving Liberia.
"We praise God for the news that Kent's condition is improving," said a Sunday statement from Samaritan's Purse.
Brantly, the first known patient with the deadly virus to be treated on U.S. soil, landed at Dobbins Air Reserve Base in Georgia on Saturday and was quickly rushed to Atlanta's Emory University Hospital.
He's one of two Americans sickened by the deadly viral hemorrhagic fever last month while on the front lines of a major outbreak in West Africa.
Video from Emory showed someone in a white, full-body protective suit helping a similarly clad person emerge from the ambulance and walk into the hospital.
Emory has said it will treat Brantly and fellow missionary Nancy Writebol in an isolation unit.
Phoenix Air says its highly specialized air ambulance, equipped with an isolation unit, departed Georgia for Liberia on Sunday evening to pick up Writebol, according to company spokesman Dent Thompson. Thompson said the flight is scheduled to land back in Georgia on Tuesday.
Brantly's wife, parents and sister cried when they saw him on CNN walking from the ambulance into the hospital, another representative of Samaritan's Purse said on condition of anonymity. His wife, Amber, later said she was relieved that her husband was back in the United States and was "confident that he is receiving the very best care."
"I was able to see Kent today. He is in good spirits," she said Sunday. "He thanked everyone for their prayers and asked for continued prayer for Nancy Writebol's safe return and full recovery."
Amber Brantly visited her husband along with their daughter in Liberia, but Frieden said on "Face the Nation" that "that they did not have contact with him when he was sick, so it does not appear that they would be at risk."
Brantly, who has ties to Texas and Indiana, and Writebol, of North Carolina, became sick while caring for Ebola patients in Liberia, one of three West African nations hit by an outbreak.
Treatment in isolation
This will be the first human Ebola test for a U.S. medical facility. The patients will be treated at an isolated unit where precautions are in place to keep such deadly diseases from spreading, unit supervisor Dr. Bruce Ribner said.
Everything that comes in and out of the unit will be controlled, Ribner said, and it will have windows and an intercom for staff to interact with patients without being in the room.
Ebola doesn't spread through airborne or waterborne methods. It spreads through contact with organs and bodily fluids such as blood, saliva, urine and other secretions of infected people.
There is no FDA-approved treatment for Ebola, and Emory will use what Ribner calls "supportive care." That means carefully tracking a patient's symptoms, vital signs and organ function and taking measures, such as blood transfusions and dialysis, to keep patients stable.
"We just have to keep the patient alive long enough in order for the body to control this infection," Ribner said.
Writebol was given an experimental serum this week, Samaritan's Purse said, though its purpose and effects weren't immediately publicized.
The Ebola virus causes viral hemorrhagic fever, which refers to a group of viruses that affect multiple organ systems in the body and are often accompanied by bleeding.
Early symptoms include sudden onset of fever, weakness, muscle pain, headaches and a sore throat. They later progress to vomiting, diarrhea, impaired kidney and liver function -- and sometimes internal and external bleeding.
Bruce Johnson, president of SIM USA, a Christian mission organization with which Writebol also is linked, said Saturday that both were seriously ill but stable.
"My last report (on Brantly) was yesterday. ... He was ambulatory, being able to talk, converse and get up. So that was encouraging," Johnson said Saturday morning.
On Writebol, Johnson said: "She's responsive, and we're encouraged at how she's doing."
Emory's isolation unit was created with the Centers for Disease Control and Prevention, based down the road. It aims to optimize care for those with highly infectious diseases and is one of four U.S. institutions capable of providing such treatment.
The World Health Organization reports that the outbreak in Liberia, Sierra Leone and Guinea is believed to have infected 1,323 people and killed more than 729 this year, as of July 27.
Fear, conspiracy theories
As officials worked to bring the two Americans home, the idea of intentionally bringing Ebola into the United States has rattled many nerves.
"The road to hell was paved with good intentions," wrote one person, using the hashtag #EbolaOutbreak. "What do we say to our kids When they get sick& die?"
On the website of conspiracy talker Alex Jones, who has long purported the CDC could unleash a pandemic and the government would react by instituting authoritarian rule, the news was a feast of fodder.
"Feds would exercise draconian emergency powers if Ebola hits U.S.," a headline read on infowars.com.
Ribner repeatedly downplayed the risk for anyone who will be in contact with Brantly or Writebol.
"We have two individuals who are critically ill, and we feel that we owe them the right to receive the best medical care," Ribner said.
The fight against Ebola
All concerns about the United States pale in comparison to the harsh reality in the hardest-hit areas.
Even in the best-case scenario, it could take three to six months to stem the epidemic in West Africa, said Frieden.
There's no vaccine, though one is in the works.
The National Institutes of Health plans to begin testing an experimental Ebola vaccine in people as early as September. Tests on primates have been successful.
So far, the outbreak is confined to West Africa. Although infections are dropping in Guinea, they are on the rise in Liberia and Sierra Leone.
On Saturday, Ebola claimed the life of a medical director at a hospital in Liberia's capital. A Saint Joseph's Hospital statement said Dr. Patrick Nshamdze tested positive July 29 after being sick for two weeks.
In the 1990s, an Ebola strain tied to monkeys -- Ebola-Reston -- was found in the United States, but no humans got sick from it, according to the CDC.
Sierra Leone deploys military; screens passengers
In Sierra Leone, where government officials have asked citizens to stay away from work, the military has deployed at least 750 infantry and military medical officials to 13 locations, military spokesman Col. Michael Samoura said Sunday.
Meanwhile, health officials are screening incoming and outgoing passengers at the country's main international airport with a device that takes people's temperature from their eyes at a distance, CNN's David McKenzie reports.
McKenzie, who arrived Sunday at Freetown's Lungi International Airport, said anyone showing signs of fever are taken away to have their blood tested for Ebola, he said.
Dr. Kent Brantly answered a calling.
That's what friends and colleagues say about the man who garnered national headlines when he became the first known Ebola hemorrhagic fever patient in the United States.
Brantly, 33, arrived Saturday in Atlanta from Liberia, where he and another American missionary worker contracted the deadly virus while caring for Ebola patients.
From an early age, Brantly was driven by his faith in God to make a difference, friends and former colleagues said. He took mission trips to Uganda, Honduras, Nicaragua, Tanzania and Haiti, they said.
"He intended to be a missionary before he became a doctor," friend Kent Smith, an elder at Southside Church of Christ in Fort Worth, Texas, told CNN.
"Eventually, he decided medical mission is what he wanted to do."
Brantly went to Liberia with his wife and two children last year to serve a two-year fellowship through Samaritan's Purse post-residency program.
He was there initially to practice general medicine. But when the Ebola outbreak began, he took on the role of medical director for the Samaritan's Purse Ebola Consolidated Case Management Center in Monrovia. It's there that he tested positive for the virus, according to the evangelical Christian relief charity.
There is no known cure or vaccine for Ebola, and it has a mortality rate of up to 90%.
Brantly is in an isolation ward at Emory University Hospital, near the headquarters for the U.S. Centers for Disease Control and Prevention.
Doctor put sick patients first
The news Brantly contracted Ebola has prompted many to ask why would he put himself at risk.
The answer might be difficult for some to understand, his former college and medical school professor wrote in an op-ed published this week in The Indianapolis Star.
"Simply put, he would say that he had been called to care for the patients in Liberia," Richard Gunderman wrote in the newspaper.
None of it has been surprising to Smith, who first met Brantly five years ago at church.
"When he first started coming to our church, he and his wife made it clear ... they were committed to medical missions," he said.
Before heading to Liberia in October 2013, Brantly did his residency at John Peter Smith Hospital in Fort Worth.
'What do I bring to the table?'
"We're kind of proud that there was a hero out there trying to do his best to make life better for other folks under the circumstances," a physician who knows him, Dr. Paul Pepe of Dallas' UT Southwestern Medical Center, told CNN affiliate WFAA this week.
Brantly attended high school in Indianapolis before graduating from Abilene Christian University (Texas) in 2003 and Indiana University's medical school in 2009.
While at Abilene Christian, he spent a summer interning overseas with a program focused on vocational missions experiences, ACU's online alumni magazine reported.
"Everyone here who has been connected with Kent knows him to be someone who is very compassionate, considerate and always upbeat in all he does," the program's director, Dr. Gary Green, told the magazine.
"... Kent's the kind of guy who would weigh benefits versus risk, then try to take himself out of the equation so that he would be thinking, 'What do I bring to the table? Is the risk worth taking because I can benefit so many people?'"
It perhaps may explain why when only one dose of an experimental serum to treat Ebola was made available this week in Liberia that Brantly turned it down and asked that it be given to his colleague.
"I would have been surprised if he had not done that," Smith said.
In an e-mail this week from Monrovia, Brantly told a fellow doctor at John Peter Smith Hospital that he is "terrified," according to The Indianapolis Star.
"I'm praying fervently that God will help me survive this disease," Brantly said in an e-mail to Dr. David McRay, the newspaper reported.
Though Brantly's wife and children had been in Liberia with him, they were in the United States when he became ill.
"Many people have been asking how I am doing," Amber Brantly said in a statement released earlier this week. "The children and I are physically fine."
The CDC has said neither Brantly's wife or his children are symptomatic.
Brantly's wife, parents and sister cried when they saw him on CNN, walking from the ambulance into the hospital, a family representative said on condition of anonymity. His wife, Amber, later said she was relieved that her husband was back in the United States.
"I spoke with him, and he is glad to be back in the U.S.," she said in statement sent to CNN. "I am thankful to God for his safe transport and for giving him the strength to walk into the hospital."
Brantly's wife visited with him from behind a glass wall for about 45 minutes, the family representative said. Kent Brantly was described as being "in great spirits and so grateful."
Meanwhile, we're learning a retired American doctor who was working with Ebola patients in West Africa returned to the United States -- and put himself in quarantine.
Dr. Alan Jamison volunteered in the Liberian capital of Monrovia this month as part of an international medical group. He returned to the United States on July 25, according to Medical Teams International, the organization he worked with.
MTI declined to discuss details of how Jamison traveled back to the United States, including whether he was on a commercial flight.
Jamison, 69, said he's had no symptoms of the deadly virus, but has been in seclusion since he returned to his hometown of Morristown, Tennessee.
He plans to be in isolation for 21 days, which is the incubation period for the disease -- or the time between infection and onset of symptoms.
"My last encounter with a patient who had Ebola was on July 19," he said. "I contacted the Centers for Disease Control and Prevention on my arrival ... and informed them I had been in West Africa and my history."
The father of three said his daughter picked him up from the airport and dropped him at home, where he's quarantined himself and has had no contact with anyone since.
"I'm feeling normal and doing the typical things a person would do in their home," he said. " I have my family who can bring me food if I need anything, and they would not enter the house. They can leave items outside the home."
Ebola spreads through contact with organs and bodily fluids such as blood, saliva, urine and other secretions of infected people.
Patients are only contagious when they show symptoms, not during the incubation period, according to the World Health Organization.
"I was not concerned that I was contagious when I left Africa, and not concerned at this time because I have no symptoms of the disease," Jamison said.
The retired pediatrician said he was volunteering with Medical Teams International.
"It was very stressful and emotional to see these things in Liberia," Jamison said.
Liberia is one of three nations battling an outbreak of Ebola. The World Health Organization says Ebola has been confirmed or suspected to have infected more than 1,300 people, with more than 700 deaths in West Africa this year.
So far, the disease has been confined to Liberia, Sierra Leone and Guinea. One man died in quarantine in Nigeria after leaving Liberia.
Two American medical workers infected in West Africa will receive treatment in Atlanta.
Dr. Kent Brantly arrived in Georgia on Saturday aboard a specially equipped plane and was taken to Emory University Hospital.
The plane is headed to Liberia to retrieve the other American, fellow missionary Nancy Writebol.
The treatment of the patients will be conducted under strict safety protocols, U.S. officials said.
There's no cure for Ebola. The most common approach is to support organ functions and keep up bodily fluids such as blood and water long enough for the body to fight off the infection.
Despite the risks, Jamison said he'd return to West Africa to help combat Ebola.