A second Texas health care worker who provided care for Ebola victim Thomas Eric Duncan has contracted the virus, according to preliminary test results released early Wednesday. The worker reported a fever Tuesday and was immediately isolated at the Texas Health Presbyterian Hospital in Dallas, state health officials said in a statement. Confirmatory testing will be carried out by the Centers for Disease Control and Prevention in Atlanta. "Health officials have interviewed the latest patient to quickly identify any contacts or potential exposures, and those people will be monitored," the Texas Department of State Health Services said. "The type of monitoring depends on the nature of their interactions and the potential they were exposed to the virus." It is the third case diagnosed in the U.S.

The worker was among those who took care of Duncan, who died a week ago after he was diagnosed with Ebola earlier this month. The first Texas Health Presbyterian nurse to become infected, Nina Pham, said in a statement Tuesday that she was "doing well" and grateful for her care. The CDC described the latest case involving a health care worker as a "serious concern." In a statement, the CDC added it was "not unexpected that there would be additional exposures." On Tuesday, the CDC's director admitted mistakes were made and said a quicker response might have prevented the virus spreading to hospital workers. A union representing nursesa also criticized the hospital, saying that protocols to protect workers were not in place when Duncan was diagnosed. "There was no advance preparedness on what to do with the patient, there was no protocol, there was no system," National Nurses United said in a statement. Ebola is spread through direct contact with bodily fluids of a sick person or exposure to contaminated objects such as needles. People are not contagious before symptoms such as fever develop.

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Second health care worker tests positive for Ebola in Texas: http://t.co/gz4P4QXTfC — DSHS Press Office (@TexasDSHS) October 15, 2014

CDC experts will answer questions on #Ebola in a live Q&A, 10/15, 4PM ET. Follow our CDC Facebook page to participate pic.twitter.com/zGLDfsck9i — CDC (@CDCgov) October 14, 2014

Thank you for your continued support of Texas Health Presbyterian Hospital Dallas and for all of our caregivers on the front lines. — TexasHealthResources (@texashealth) October 14, 2014

- Alastair Jamieson