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A health care worker at Texas Health Presbyterian Hospital who cared for dying Ebola patient Thomas Eric Duncan, has tested positive for the virus after a preliminary test, officials said early Sunday. If confirmed, it would be the first known person-to-person transmission of the disease in the United States.

Confirmatory testing of the second case on U.S. soil will be conducted by the Centers for Disease Control and Prevention in Atlanta, the statement from the Texas Department of State Health Services said.

The worker reported a fever late Friday and was isolated and referred for testing. "We knew a second case could be a reality, and we've been preparing for this possibility," said Dr. David Lakey, commissioner of the Texas Department of State Health Services. "We are broadening our team in Dallas and working with extreme diligence to prevent further spread."

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The statement added that people who had contact with the health care worker after symptoms emerged "will be monitored based on the nature of their interactions and the potential they were exposed to the virus."

The development came hours after New York's JFK Airport began an Ebola screening program, taking the temperatures of passengers arriving from three West African Countries.

Duncan on Wednesday became the first person to die of Ebola in the U.S. He was re-admitted for treatment after initially being sent home from the hospital despite having a fever of 103 degrees, his family said.

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Texas Health Dallas employees attended a prayer service for Mr. Thomas Eric Duncan on Wednesday, Oct. 8. pic.twitter.com/bZ2hhIHEN6 - TexasHealthResources (@texashealth) October 9, 2014

- Alastair Jamieson and Maggie Fox