WASHINGTON, Aug. 2 -- One of the two Americans who contracted the Ebola virus while treating patients in Liberia was brought back to the United States for treatment Saturday, the aid group he worked for said.

A private plane equipped with a special containment unit for doctor Kent Brantly arrived at Dobbins Air Force Base in Atlanta Saturday morning, North Carolina-based Christian organization Samaritan's Purse said in a statement.

The patient was then transported to Emory University Hospital where has an isolation unit set up in collaboration with the U.S. Centers for Disease Control and Prevention (CDC) to treat patients who are exposed to certain serious infectious diseases, the group said.

A second American, missionary Nancy Writebol who was also infected with Ebola in Liberia, is expected to arrive in Atlanta within the next few days, it said.

"They are alive and now have access to the best care in the world," said Franklin Graham, president of Samaritan's Purse. "We are extremely thankful for the help we have received."

Earlier, the aid group said both patients are "in serious but stable condition."

Amber Brantly, wife of Kent Brantly, said his husband walked into the hospital.

"It was a relief to welcome Kent home today," she said in a statement. "I spoke with him, and he is glad to be back in the U.S. "

Some Americans, such as business magnate Donald Trump, have asked to keep Ebola patients out of the United States.

"The U.S. must immediately stop all flights from EBOLA infected countries or the plague will start and spread inside our 'borders. ' Act fast!" Trump tweeted Saturday. "The fact that we are taking the Ebola patients, while others from the area are fleeing to the United States, is absolutely CRAZY -- Stupid pols."

But U.S. health authorities dismissed the criticism.

"Any U.S. hospital following CDC's infection control recommendations can safely managing a patient" with Ebola, CDC Director Tom Frieden tweeted Saturday, apparently responding to remarks like Trump's.

"In the past decade, there have been 5 patients with hemorrhagic fevers similar to #Ebola in the U.S., and none has spread the infection," he said.

Emory Healthcare also said it has learned that "there has been much discussion "about bringing patients with Ebola back into the country.

However, "Emory University Hospital physicians, nurses and staff can treat them safely and effectively, and we are honored to have the privilege of caring for these patients who contracted Ebola while serving on a humanitarian mission," Emory Healthcare said in a statement.

"Emory University Hospital is one of the very few hospitals in the country equipped to provide their care. Our highly trained staff and physicians are ready to receive both patients and provide them outstanding care of the highest quality," it said.

It added the patients will be housed in a physically separate and highly specialized unit that was intentionally designed and constructed to receive patients such as these.

On Thursday, the U.S. government issued a warning against nonessential travel to West African nations of Guinea, Liberia and Sierra Leone, saying it reflects the "worsening" Ebola outbreak in this region.

The hemorrhagic virus can kill up to 90 percent of those who become infected, and the fatality rate in the current epidemic is about 60 percent.

The outbreak, by far the largest in the nearly 40-year history of the disease, has killed 729 people and affected more than 1,300 this year, according to the World Health Organization.