The second Dallas health care worker to test positive for Ebola took a flight on Monday from Cleveland to the Dallas area the day before she reported symptoms of the disease, federal health officials said Wednesday.

The head of the federal Centers for Disease Control and Prevention, Dr. Thomas R. Frieden, said that the worker should not have been on a commercial flight, but that the risk to the 132 passengers on the plane was “extrememly low.”

The health care worker, identified as Amber Joy Vinson, reported having a fever on Tuesday and was isolated a short time later at Texas Health Presbyterian Hospital.

“She should not have travelled, should not have been allowed to travel by virtue she was in an exposed group,” Dr. Frieden said at a news conference on Wednesday. But, he added, “she did not vomit, she was not bleeding” so that it was highly unlikely that any others on the flight had contracted the virus.