(CNN) -- A second health care worker who cared for an Ebola patient at a Dallas hospital has contracted the virus herself.
The worker, a woman who lives alone, was quickly moved into isolation at Texas Health Presbyterian Hospital, authorities said Wednesday.
The news cast further doubt on the hospital's ability to handle Ebola and protect employees. It's the same hospital that initially sent Thomas Eric Duncan home, even though he had a fever and had traveled from West Africa. By the time he returned to the hospital, his symptoms had worsened. He died while being treated by medical staff, including the two women who have now contracted the disease.
"I don't think we have a systematic institutional problem," Dr. Daniel Varga, chief clinical officer of Texas Health Resources, told reporters Wednesday, facing questions about the hospital's actions.
Medical staff "may have done some things differently with the benefit of what we know today," he said, adding, "no one wants to get this right more than our hospital."
People in the health care worker's office building were informed when officials went door to door, and also through early morning reverse 911 calls, officials said.
The health care worker had no pets, authorities said.
Seventy-five health care workers in Dallas are being monitored for any Ebola symptoms, Varga said.
Separately, Dallas County Judge Clay Jenkins, who is overseeing the response efforts, said 48 other people in the community still are being monitored after having contact with Duncan, who was Dallas' first Ebola patient. Those 48 are asymptomatic, and Sunday will mark the end of the window in which they could get sick.
The second worker reported a fever Tuesday and was immediately isolated, health department spokeswoman Carrie Williams said. The virus is not contagious before there are symptoms.
A preliminary Ebola test was done late Tuesday at the state public health laboratory in Austin, and the results came back around midnight. A second test will be conducted 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 health department said.
The worker's apartment and car will be cleaned Wednesday, Dallas Mayor Mike Rawlings said.
An official close to the situation says that in hindsight, Duncan should have been transferred immediately to either Emory University Hospital in Atlanta or Nebraska Medical Center in Omaha.
Those hospitals are among only four in the country that have biocontainment units and have been preparing for years to treat a highly infectious disease like Ebola.
"If we knew then what we know now about this hospital's ability to safely care for these patients, then we would have transferred him to Emory or Nebraska," the official told CNN senior medical correspondent Elizabeth Cohen.
"I think there are hospitals that are more than ready, but I think there are some that are not."
The latest infection marks the second-ever transmission of Ebola in the United States. Both stemmed from Texas Health Presbyterian Hospital.
Late last week, nurse Nina Pham
tested positive for Ebola. She also took care of Duncan, the first person to be diagnosed with Ebola in the United States. Duncan died last week.
On Tuesday, Pham said she was doing well.
"I am blessed by the support of family and friends, and am blessed to be cared for by the best team of doctors and nurses in the world," she said.