Confirmatory testing will be conducted by the Centers for Disease Control and Prevention in Atlanta.
The employee helped care for Thomas Eric Duncan, the first person diagnosed with Ebola in the United States."We knew a second case could be a reality, and we've been preparing for this possibility," Dr. David Lakey, commissioner of the Texas Department of State Health Services, said in a statement Sunday morning.
"We are broadening our team in Dallas and working with extreme diligence to prevent further spread."
If confirmed by the CDC, the health care worker's case would mark the second diagnosis of Ebola ever in the United States.
Globally, the disease has wrought catastrophic consequences.