US President Barack Obama has played down the chance of an Ebola outbreak in the US, after a second nurse became infected caring for a patient.

Amber Vinson was not supposed to travel on an aeroplane, health officials said

He said the risk of Americans getting the virus was "extremely low" but more needed to be done to help West Africa.

Amber Vinson, 29, fell ill on Tuesday, after treating Liberian Thomas Eric Duncan, who died a week ago in Dallas.

US health officials are seeking to trace the 132 people who flew on a plane with her the day before.

The US Centers for Disease Control and Prevention (CDC) said it wanted to interview the passengers on Frontier Airlines flight 1143 from Cleveland, Ohio, to Dallas, Texas on Monday.

An unnamed federal official has told US media the nurse called the CDC before boarding to report a temperature of 99.5F and to say she was getting on a plane.

Ms Vinson is the second nurse to become infected after treating Duncan at the Texas Health Presbyterian Hospital.

A nurses' union has said healthcare workers were not given full protection and had parts of their skin exposed.

More than 70 medics who may have come in contact with Duncan at the hospital are being monitored for symptoms.

Mr Obama cancelled a political campaign trip to meet Cabinet officials involved in the Ebola response both in the US and in West Africa.

The virus has killed more than 4,000 in the region, mostly in Liberia, Guinea and Sierra Leone.

And while reassuring Americans about the risks to them, the president was clear that more needed to be done in West Africa.

"I am absolutely confident that we can prevent a serious outbreak of the disease here in the United States but it becomes more difficult to do so if this epidemic of Ebola rages out of control in West Africa."

In promising a "much more aggressive" monitoring of Ebola cases in the US, he reaffirmed plans to send a "Swat team" of experts to any hospital that reported an infection.

It is still unclear how Ms Vinson and the other infected nurse, Nina Pham, contracted the virus while following the safety procedures.

A national nurse union said the health workers treating Duncan had not been properly equipped and called for all health workers treating Ebola patients to receive full protective suits and training from hospitals.

Union director RoseAnn DeMoro said staff treated him for days without the necessary protective gear, and hazardous waste was allowed to accumulate.

The CDC has appointed a "site manager" in Dallas to standardise the protective equipment and supervise the method of putting it off and on.

Questions have also been raised about how Ms Vinson was allowed to board a flight, even though she was being monitored for signs of Ebola.

Source: BBC