US President Barack Obama has played down the chance of an Ebola outbreak in the US, saying the risk of Americans getting the virus was "extremely low".
He was speaking after a second US nurse became infected after treating a Liberian who died a week ago in Dallas.
Meanwhile, a UN chief has warned that West Africa faces a potential food crisis because of the Ebola crisis.
The disease has killed about 4,500 people so far, mostly in Liberia, Guinea and Sierra Leone.
In the US, health officials are seeking to trace 132 people who flew on a plane with Amber Vinson the day before she fell ill.
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 that Ms Vinson, 29, called the CDC before boarding to report a temperature of 99.5F (37.5C) and to say she was getting on a plane.
She is the second nurse to become infected after treating Thomas Eric Duncan at the Texas Health Presbyterian Hospital.