US President Barack Obama said late Thursday that he may appoint an Ebola czar to manage the growing health crisis.

The president said it "may make sense for us to have one person ... so that after this initial surge of activity, we can have a more regular process just to make sure that we're crossing all the T's and dotting all the I's" after a meeting in Washington, CNN reported.

The administration also announced Thursday that it would call up as many as 4,000 US troops to fight the spread of the disease in Africa. "Operation United Assistance" would provide "civilian-led humanitarian assistance and consequence management support".

The announcements come after news that a second nurse from Texas who has contracted the deadly disease said she was allowed to board a plane from Ohio to Texas.

The nurse, Amber Vinson, 29, flew from Cleveland to Dallas on Monday, the day before she was diagnosed with Ebola, the US Centers for Disease Control and Prevention said. Vinson said she told a US health official that she had a slight fever. Vinson told the CDC her temperature was 37.5 C. Since that is below the CDC's temperature threshold of 38 C, she was not barred from flying, a source said.

The chances that other passengers were infected were minimal because Vinson did not vomit on the flight and was not bleeding but she should not have been aboard, CDC Director Thomas Frieden said.

Vinson was isolated immediately after reporting a fever on Tuesday, officials at the Texas Department of State Health Services said.

The nurse had treated Liberian patient Thomas Eric Duncan, who died of Ebola on Oct 8 and was the first patient diagnosed with the virus in the US.

Vinson was transferred to Emory University Hospital in Atlanta by air ambulance and is being treated in a special isolation unit. Three other people have been treated there and two have been discharged, the hospital said in a statement.

Television images showed Vinson walking from an ambulance to an Emory Hospital door with an escort, both of them in protective clothing.

Vinson, a worker at Texas Health Presbyterian Hospital in Dallas, took a Frontier Airlines flight to Cleveland from Dallas/Fort Worth International Airport on Friday.

She returned to Dallas on Monday aboard another Frontier flight. The CDC said it is asking the more than 130 passengers on this flight to call a hotline.

Frontier Airlines CEO David Siegel said in a letter to employees that the CDC notified the airline on Wednesday morning that Vinson had tested positive for Ebola, then later said she may have been symptomatic while on board the flight.

Frontier took the plane out of service on Wednesday morning for cleaning and put two pilots and four flight attendants on paid 21-day leave as a precaution, the letter said, even though CDC guidance stated the crews were safe to fly.

Between the initial flight on Friday and Wednesday, the plane made at least five more flights, according to the letter.

US Federal Aviation Administration chief Michael Huerta said the government would decide whether to issue a travel ban from West African nations "on a day-to-day basis". Numerous US lawmakers have called for travel restrictions on the African countries most affected by Ebola: Liberia, Sierra Leone and Guinea.

Obama said he wasn't philosophically opposed to a ban but was concerned that such restrictions could lead to people finding other ways into the US, which could make the crisis worse.

REUTERS, AP, XINHUA contributed to this story

(China Daily USA 10/17/2014 page2)