The US Centers for Disease Control and Prevention spoke with the woman by phone when she was at a Cleveland, Ohio airport on October 13, the source told AFP on condition of anonymity.
At that time, she reported a temperature of 99.5 Fahrenheit (37.5 Celsius). The threshold that would have kept her from flying was 100.4 F (38 C).
"My understanding is she reported no symptoms to us," CDC director Thomas Frieden told lawmakers on Thursday.
Another nurse, Nina Pham, at Texas Health Presbyterian Hospital Dallas was diagnosed with Ebola on October 12, a day before Vinson boarded the flight home from visiting family in Ohio.
The CDC is trying to contact 132 people who took the same Frontier Airlines flight as the Vinson on October 13 from Ohio to Texas.
Some schools in Ohio and Texas closed on Thursday after learning that staff or students may have been on the same plane.
The latest case has led health authorities to consider a travel ban for health care workers who have had potential exposures to Ebola, a source with knowledge of the matter told AFP.
"The discussion is ongoing right now. We believe that it is now more important than ever that a public health official be observing these people," said the source, who spoke on condition of anonymity.
Frieden told reporters on Wednesday that Vinson "was in a group of individuals known to have exposure to Ebola. She should not have traveled on a commercial airline."
"She did not vomit. She was not bleeding. So the level of risk of people around her would be extremely low, but because of that extra margin of safety we will be contacting them all," Frieden said.
