A second health care worker at a Dallas hospital who tested positive for Ebola was isolated within "90 minutes" of her temperature being taken, officials said Wednesday.

The new case suggests measures at the Texas Health Presbyterian Hospital in Dallas were unable to prevent the virus from spreading beyond a very sick Thomas Eric Duncan, the Liberian who died there last week.

The worker developed a fever on Tuesday, Dallas County Judge Clay Jenkins told a news conference.

“Within 90 minutes of taking her temperature she was isolated in the hospital,” Jenkins said early Wednesday. “And we hope and pray that, like Nina, she will get on a good track.” Over the weekend 26-year-old nurse Nina Pham was diagnosed with the virus.

The Centers for Disease Control and Prevention and Frontier Airlines have confirmed the new patient returned to Dallas-Fort Worth on Monday evening — the day before she reported symptoms. Because of the proximity in time between the evening flight and first report of illness the following morning, CDC is reaching out to passengers who flew on Frontier Airlines flight 1143. The patient flew to Cleveland on Oct. 8, according to Cleveland health officials.

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The health-care worker exhibited no signs or symptoms of illness while on the flight, according to the Frontier Airlines crew.

Jenkins described the woman as "a heroic person, a person who is dedicating her life to serving others."

The hospital has been fighting allegations by some staff and by an outside nurses union that it didn’t do enough to protect workers. It’s also been fighting off criticism that Duncan, who has died, was mistakenly sent away when he first sought care. He later became very ill and was returned to the hospital by ambulance.

When asked about the criticism on Wednesday, Texas Health Resources chief clinical officer Dr. Daniel Varga said: "I don't think we have a systematic, institutional problem."

Health experts say that Ebola patients become progressively more infectious as they get sicker, and the virus is spread in vomit, diarrhea and other bodily fluids. Quick isolation of a patient before they start to show these symptoms can help prevent spread.

The latest worker infected lives alone and has no pets. According to Varga, 75 more health care workers are being monitored. Federal health officials said Tuesday that their response to the original Dallas case could have been more robust.

The Centers for Disease Control and Prevention said it has sent a team to the hospital to help improve infection control there and to help train staff. An officer will be on-site at all times to make sure workers put on and take off protective gear in the right way to prevent contamination.

IN-DEPTH

— Maggie Fox and Jason Cumming