Medical experts need to rethink how highly infectious diseases are handled in the US, according to a US health official, after a Dallas health worker contracted Ebola despite wearing protective gear while caring for a dying Liberian patient.

As an outbreak of the deadly virus spread beyond West Africa, hospitals and nursing associations across the US were taking a closer look at how prepared they were to handle such infections.

"We have to rethink the way we address Ebola infection control. Even a single infection is unacceptable," Dr Thomas Frieden, director of the US Centres for Disease Control and Prevention (CDC), said.

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

Nina Pham, 26, the Texas nurse, repeatedly visited Thomas Eric Duncan's room from the day he was admitted to the intensive care unit until the day before he died, medical records show.

She and other health workers wore protective gear, including gowns, gloves, masks and face shields - and sometimes full-body suits - when caring for Duncan, but she became the first person to contract the disease within the US.

Pham's family told WFAA-TV in Dallas on Monday that she was the health worker with Ebola.

A rector at her family's church, Hung Le, told the Associated Press news agency that Pham's mother told him Pham has the virus.

'In isolation and stable'

Pham was among about 70 hospital staffers who were involved in Duncan's care after he was hospitalised, according to the records.

She was monitoring her own temperature and went to the hospital Friday night as soon as she discovered she was running a low fever.

She is in isolation and in stable condition, health officials said.

By Monday evening, she had received a transfusion of plasma from a doctor who survived the virus, according to her pastor and the nonprofit medical mission group Samaritan's Purse.

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Public-health authorities have since intensified their monitoring of other Dallas hospital workers who cared for Duncan.

Frieden said he would not be surprised if another hospital worker who cared for Duncan becomes ill because Ebola patients become more contagious as the disease progresses.

He has said a breach of protocol led to the nurse's infection, but officials are not sure what went wrong. Pham has not been able to point to any specific breach.

The CDC now is monitoring all hospital workers who treated Duncan and planned to "double down" on training and outreach on how to safely treat Ebola patients, Frieden said.

When asked how many health workers are being checked, Frieden said officials "don't have a number".

Health officials have relied on a "self-monitoring" system when it comes to US health workers who care for isolated Ebola patients and wear recommended protective equipment.

They expect workers to report any potential exposures to the virus and watch themselves for symptoms.

Besides the workers, health officials continue to track 48 people who were in contact before Duncan was admitted to the hospital and placed in isolation.

They are monitoring one person the nurse was in contact with while she was in an infectious state. None has exhibited symptoms, Frieden said.

Obama's appeal

Meanwhile, in Washington DC, President Barack Obama has urged his top national security and public health officials to incorporate lessons from the Duncan case into the US response plans to the deadly virus.

He also called on the international community to deliver assistance more quickly to the countries of West Africa that are struggling against the disease.

Obama held a meeting with senior advisers in the Oval Office on Monday and placed calls to Ban Ki-moon, the UN chief, and French President Francois Hollande.

Obama met Susan Rice, national security adviser; Sylvia Burwell, health and human services secretary; and Lisa Monaco, his top aide on homeland security and counterterrorism issues.

The CDC's Frieden joined the meeting by phone.

The White House said that in his call with Ban, Obama "stressed the need for all UN member states to support the UN appeal, and to provide the personnel, equipment, and supplies required to stop the epidemic at its source and halt the devastating impact of this crisis on the affected countries and their citizens".

Elsewhere, a brief scare at Boston's Logan International Airport caused emergency crews in protective gear to remove five passengers with flu-like symptoms from Emirates flight 237 from Dubai, but the CDC later said there was no Ebola threat.

Source: Agencies