A nurse infected with Ebola may have had symptoms sooner, authorities say, and an airline is notifying passengers who were on the same flights she took from Dallas to Cleveland.

In addition to Amber Vinson's return trip, Frontier Airlines is also reaching out to others who were in five subsequent flights that used the same plane she flew in from Cleveland.

Vinson was hospitalized Tuesday, a day after she took Frontier Airlines flight 1142 from Cleveland to Dallas.

Vinson, a nurse at Texas Health Presbyterian Hospital in Dallas, was part of a team that treated Thomas Eric Duncan, the first person diagnosed with Ebola in the United States. He died last week.

Frontier Airlines says it is notifying up to 800 passengers linked to Vinson's flights. They include those aboard her Dallas-to-Cleveland flight on October 10, a return flight four days later and five subsequent trips by the plane used in the latter flight.

The expanded efforts came after officials said she may have shown symptoms of the virus four days before authorities first indicated. Ebola is contagious when someone is symptomatic.

At first, authorities indicated Vinson had a slightly elevated temperature of 99.5 degrees Fahrenheit, which was below the fever threshold for Ebola, but didn't show any symptoms of the disease while on her Monday flight.

But Dr. Chris Braden of the Centers for Disease Control and Prevention took a more cautionary approach Thursday.

"We have started to look at the possibility that she had symptoms going back as far as Saturday," he said. "We can't rule out (that) she might have had the start of her illness on Friday."

Based on the new information, he said, the contacts were expanded to those aboard her flight out of Dallas.

Her uncle, Lawrence Vinson, said Thursday night that his niece didn't feel sick until Tuesday morning, when she went to the hospital with a temperature of 100.3 degrees (which is still below the CDC's Ebola threshold).

(CNN)