A second health care worker has tested positive for Ebola, the Texas Department of State Health Services said Wednesday. The nurse is the third person to be diagnosed with the Ebola virus in the U.S.

At a press conference Wednesday, Dallas County Judge Clay Jenkins said the nurse reported a fever on Tuesday and has been placed in isolation at Texas Health Presbyterian Hospital in Dallas, along with Nina Pham, another nurse who tested positive for the virus on Sunday. Both nurses were involved in the care of Thomas Eric Duncan, who died from Ebola last week.

CDC director Tom Frieden said the new patient will be transferred to Emory hospital in Atlanta.

Jenkins said Texas Presbyterian Hospital is preparing for more cases of Ebola. 

"We are preparing contingencies for more, and that is a very real possibility,”  Jenkins said.

Daniel Varga, chief clinical officer for Texas Health Presbyterian Hospital, said the nurses contracted the virus after being exposed to Duncan, even though they were wearing protective equipment. 

“There was an exposure somewhere, sometime in the treatment of Mr. Duncan," Varga said. “Let’s be clear: We’re a hospital that may have done some things different with the benefit of what we know today. But make no mistake, no one wants to get this right more than our hospital."

The CDC and Frontier Airlines have confirmed in a statement that the new patient took a flight from Dallas-Fort Worth to Cleveland on Oct. 10 and returned to Dallas-Fort Worth on Monday evening, the day before she reported symptoms. The CDC is monitoring passengers who flew on the flight, even though the health care worker exhibited no signs or symptoms of illness while on the plane. 

Frieden said the new patient should not have traveled on a commercial airline, and that workers having contact with an Ebola patient will not be allowed to travel. 

The CDC also said it has sent a team to the hospital in Dallas to oversee infection control and monitor its use of protective equipment.