A second health care worker at Texas Health Presbyterian Hospital in Dallas, shown here, has tested positive for Ebola. More than 70 staff members at the facility were involved in the care of Thomas Eric Duncan, who died from the virus last week.

DALLAS — A Texas nurse who caught Ebola from an infected patient was no stranger to the risks of working around one of the world’s most feared viruses.

In nursing school, Nina Pham had studied microbiology and infection prevention. A classmate said students discussed Ebola in detail, even reading “The Hot Zone,” a bestselling 1994 book about the disease’s origins.

Pham continued her training after graduation, obtaining certification in critical care two months before Ebola arrived in the United States.

On Tuesday, her infection raised new questions about whether American hospitals and their staffs are adequately prepared to contain Ebola. And early today, Texas health officials announced that a preliminary test indicated another health care worker at the hospital had been infected with the disease.

The Centers for Disease Control and Prevention acknowledged that Pham might not have been infected if a special response team had been sent to Dallas immediately after the Liberian patient was diagnosed.

CDC Director Tom Frieden said the agency is creating an “Ebola response team” and bolstering training nationwide on how to respond to an Ebola case.

Pham, the first person to contract the disease within the United States, was among more than 70 staff members at Texas Health Presbyterian Hospital in Dallas involved in Thomas Eric Duncan’s care before he died last week. The 26-year-old nurse remained hospitalized Tuesday in good condition and said in a statement that she was “doing well.”

When Pham’s mother learned her daughter was caring for Duncan, Pham tried to reassure her that she would be safe.

Pham told her: “Mom, no. Don’t worry about me,” family friend Christina Tran told The Associated Press.

Duncan’s medical records, which the family shared with The Associated Press, show that Pham helped care for Duncan throughout his hospital stay, including the day he arrived in intensive care and the day before he died.

The records make numerous mentions of protective gear worn by hospital staff, and Pham herself notes wearing the gear in visits to Duncan’s room. But there is no indication in the records of her first encounter with Duncan, on Sept. 29, that Pham donned any protective gear.

Pham got her nursing degree in 2010 from Texas Christian University in Fort Worth. A school spokesman and the classmate described the curriculum. The classmate spoke on the condition of anonymity, saying she did not want to infringe on Pham’s privacy.

Two nurses from Emory University Hospital in Atlanta with special training in Ebola care are now helping to train staff at the Dallas hospital, Frieden said.