Austin (Texas), Oct 14 (IANS/EFE) Authorities have said the Dallas nurse, Nina Pham, infected with the Ebola visrus disease is "clinically stable".

At a press conference Monday, head of the US Centres for Disease Control (CDC) and Prevention, Thomas Frieden, also said that there could be new Ebola cases among the medical personnel who cared for Thomas Eric Duncan, the Liberian patient with the virus who died last Wednesday.

"We have to rethink the way we address Ebola infection control. Even a single infection is unacceptable," Frieden told reporters.

"The care of Ebola is hard. We're working to make it safer and easier," he added.

The CDC head, who after Pham was confirmed to have been infected with Ebola Sunday, said that there had been a "breach of protocol" in attending to patients with the virus, said Monday that authorities still had not been able to determine precisely how Pham became infected.

He apologised for having suggested Sunday that she herself was responsible for the breach in protocol leading to her infection.

Pham, 26, was one of the nurses at the Texas Health Presbyterian Hospital in Dallas who attended to Duncan, the first person diagnosed with Ebola outside West Africa, although he had just returned from there.