Health officials in the United States have faced intense questioning over the ‘failures’ to deal with the evolving Ebola situation in the country.

Only two people are known to have contracted the virus in the US, but a litany of missteps from health officials has raised doubts about whether they can stop a full-blown outbreak.

House Energy and Commerce Committee chairman Tim Murphy said: "The trust and credibility of the administration and government are waning as the American public loses confidence each day."

Dr Daniel Varga, chief clinical officer of the company that owns Texas Health Presbyterian Hospital in Dallas, where two nurses caught Ebola, told Thursday's hearing he was "deeply sorry".

He said it remained unclear how the two nurses contracted the disease.

Centers for Disease Control and Prevention (CDC) chief Tom Frieden told the lawmakers, meanwhile, he was not involved in the erroneous advice given to one of the nurses, Amber Vinson.

A CDC official cleared her to board a plane from Cleveland to the Dallas area, even though she had been exposed to the disease while caring for a patient.

She also told the CDC she had a temperature of 99.5 degrees (37.5C), which was slightly below the 100.4-degree threshold set by the agency.

The health agency is now trying to track down 132 other passengers who were on the Frontier Airlines flight in case they too have been infected.

Dr Frieden expressed doubt at Thursday's hearing that a travel ban from Ebola-ravaged countries, which Republicans are calling for, would be effective.

But he said they should "consider any options to better protect Americans".

Miss Vinson, 29, was one of several nurses to treat Thomas Eric Duncan, who came down with the virus and died on 8 October after travelling to Texas from Liberia.

She was already being monitored closely because a fellow nurse, Nina Pham, 26, caught Ebola after also being involved in Mr Duncan's care.

Miss Pham, who was in good condition, is being transferred to a federal facility in Maryland.

Miss Vinson was transported to an isolation unit at Emory University Hospital in Georgia a day earlier.

More than 70 other healthcare workers involved in Mr Duncan's care were being monitored.

President Barack Obama directed his administration on Wednesday to respond in a "much more aggressive way" to the US Ebola situation.

For the second day in a row he took the unusual step of cancelling trips away from Washington in order to monitor the disease response from the White House.

The death toll has passed 4,500 in West Africa, mainly in Liberia, Sierra Leone and Guinea.