The American doctor who contracted Ebola while working with an aid organization in Liberia appears to be improving, a top U.S. health official said Sunday, less than 24 hours after the doctor was admitted to an isolation unit at an Atlanta hospital for treatment.

Dr. Kent Brantly "seems to be improved from the reports we got earlier," Dr. Tom Frieden, the director of the Centers for Disease Control and Prevention, said on NBC's "Meet the Press." Authorities and doctors are still closely monitoring Brantly, who is being treated at Emory University Hospital.

Brantly's wife, Amber, told church friends in their Texas hometown that she was “rejoicing in the Lord for Kent’s arrival yesterday,” adding in an email that her husband “has a long way to go.” She asked for the congregation to continue praying for her husband, for Nancy Writebol, a second American infected with Ebola, and for those fighting the deadly disease in west Africa.

“We are heartbroken for Liberia, and ask that you please pray for God's hand of healing to reach out and contain the virus in west Africa,” she wrote.

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Ebola has no known cure and can be treated only with "supportive therapy," such as balancing the patient's fluids and electrolytes, monitoring vital signs and treating any additional infections, according to the CDC.

But Brantly may have an advantage because he was likely healthier before contracting the disease than African victims of Ebola, Frieden said. And the death rate of the outbreak that began in March is 60 percent, lower than the 90 percent rate in some previous outbreaks.

Brantly was flown in a containment-outfitted plane from Liberia to Atlanta on Saturday and then taken by ambulance to the hospital. Doctors and his family were encouraged when he walked the short distance from the ambulance to the entrance of the hospital, with the assistance of an aide, instead of being brought in on a stretcher.

The walking is a “terrific sign,” said Dr. Delos Cosgrove, president of the Cleveland Clinic, who added that the care Brantly will receive in the U.S. is better than what he would receive “anywhere in the world.”

Big day for medicine, humanitarian aid, NGO-govt agency coordination & docs, nurses, personnel who put themselves out there @emoryhealthsci — Dr. Nancy Snyderman (@DrNancyNBCNEWS) August 2, 2014

Writebol is expected to arrive at Emory within a few days, according to Samaritan’s Purse and SIM, the charity organizations with which Brantly and Writebol were working in Liberia.

While Ebola is a “formidable enemy,” the CDC and health workers are being “meticulous” about ensuring that Ebola doesn’t become a threat in the U.S., Frieden said.

“What our role is, in public health, is to make sure that if an American is coming home with an infectious disease, we protect others so that they don’t spread it,” he said.

Check out these FAQs about #Ebola and Emory’s care for these patients: http://t.co/KRaNvC8rVL — Emory Healthcare (@emoryhealthcare) August 2, 2014

While Americans infected with Ebola have the option to come home for superior treatment, those suffering from the disease in Western Africa don’t have that option, and the outbreak is only getting worse.

More than 1,300 people have been infected with Ebola in Sierra Leone, Guinea and Liberia since the outbreak began in March, according to the World Health Organization. WHO estimates that 729 people have died from the disease during the current outbreak.

In the next 30 days, the CDC plans to send 50 public health experts to the three affected countries, Frieden said Sunday. “We do know how to stop Ebola,” Frieden said. “It’s old-fashioned, plain and simple public health.”

“Increased resources, in-country medical expertise, regional preparedness and coordination,” are required to get the “unprecedented” spread under control, Dr. Margaret Chan, the director-general of WHO, said in a statement. “The countries have identified what they need, and WHO is reaching out to the international community to drive the response plan forward,” Chan said.