The director of the Centers for Disease Control and Prevention said Sunday that Americans should not fear a domestic Ebola outbreak, as a doctor infected with the deadly virus is being treated in Atlanta.

“I don't think it's in the cards that we would have widespread Ebola in this country,” CDC head Thomas Frieden said on CBS’ “Face the Nation.”

“It's not going to spread widely in the U.S.,” he added. “Could we have another person here, could we have a case or two? Not impossible. We say in medicine never say never. But we know how to stop it here. But to really protect ourselves, the single most important thing we can do is stop it at the source in Africa. That's going to protect them and protect us.”

On Saturday, American doctor Kent Brantly arrived at Emory University Hospital in Atlanta, marking the first time an Ebola patient has been brought back to the U.S. for treatment.

However, Frieden was forced to defend his agency’s capacity to contain Ebola in the wake of the CDC mishandling anthrax, smallpox and avian flu samples earlier this year.

“There were lapses in our laboratory,” Frieden conceded. “Fortunately, we identified them and reported them before anyone got harmed and before there was any release of anything into the community. But that really shows the importance of being meticulous with infection control.”