(CNN) — A health care worker at Texas Health Presbyterian Hospital in Dallas has tested positive for Ebola after a preliminary test, the state’s health agency said.
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 ever diagnosed with Ebola in the United States. Duncan died Wednesday.
“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.”
The health care worker reported a low-grade fever Friday night and was isolated, the health department said. The preliminary test result came in late Saturday.
If confirmed by the CDC, the health care worker’s case would mark the first known transmission of Ebola in the United States and the second-ever diagnosis in the country.
David Sanders, associate professor of biological sciences at Purdue University, said he thinks the CDC testing will probably support the preliminary results.
“It sounds likely that it’s positive, and it’s going to stay positive.”
Globally, the disease has wrought catastrophic consequences.
The World Health Organization estimates more than 8,300 people have contracted Ebola during this year’s outbreak. Of those, more than 4,000 have died.
Those stricken with Ebola suffer ghastly symptoms, including vomiting, diarrhea, muscle pain, fever and unexplained bleeding.
Three countries — Sierra Leone, Guinea and Liberia — have been hardest hit. And many of those who care for the ill have also come down with the disease.
The World Health Organization estimates at least 416 health care workers have contracted Ebola, and at least 233 have died.
In Liberia, health care workers are threatening to strike if their work conditions don’t improve.
The first infection outside of Africa happened in a nurse’s aide in Spain, Teresa Romero Ramos. She became sick after she helped treat an Ebola-stricken Spanish missionary.
Her case has prompted questions from fellow medical professionals about whether they are properly equipped to safely treat Ebola patients.
Spanish Ebola patient’s condition worsens, doctor says
Another search begins
For weeks, health officials have been monitoring those who had contact with Duncan before he was hospitalized and isolated.
Duncan left Liberia on September 19 and arrived in Dallas on September 20. Four days later, he began feeling ill; the following night, he went to Texas Health Presbyterian Hospital.
But despite telling a hospital worker that he had arrived from Liberia, Duncan was sent home with antibiotics. He returned a few days later and tested positive for Ebola.
It’s not clear whether the health care worker in the second Ebola case contracted the disease during Duncan’s first visit to the hospital or after he was isolated.
But now, the search begins for all the contacts whom that worker came in contact with.
“We need a whole new crew of people to do contact tracing,” said Elizabeth Cohen, CNN senior medical correspondent.
Because Ebola’s incubation period can last up to 21 days, the health care worker’s contacts will have to be monitored for three weeks.
The Texas health department said officials have interviewed the patient and are identifying any contacts or potential exposures.
“This is not an easy thing,” Cohen said. “Keeping track of large numbers of people, taking their temperature twice a day, making sure they don’t … leave town, all of that is a lot of work.”
LIVE UPDATES (Times in GMT)
(1:10) – Patient confirmed to be a Female nurse who cared for Thomas Eric Duncan, the first US Ebola patient to die of the disease
(1:20) – Police have closed off a 4-block area around the Nurse’s apartment building
(1:24) – Close contact with new patient is under isolation; 19 CDC agents looking for more people who could have had contact with the nurse