A Texan health worker who treated Ebola victim Thomas Eric Duncan before he died is also infected with the virus, according to a preliminary test.
A Texan health worker who treated Ebola victim Thomas Eric Duncan before he died is also infected with the virus, according to a preliminary test.
The unnamed woman, who is in a stable condition in an isolation ward, wore full protective gear while treating Duncan, officials in Dallas say.
If confirmed, this is the first known transmission of Ebola on US soil.
A top federal health official said there had been a clear breach of safety protocol and other cases could follow.
Dr Tom Frieden, head of the Centers for Disease Control and Prevention (CDC), said 48 people who may have had contact with Duncan were being monitored for symptoms.
He said a complete investigation would be conducted into how the infection had occurred at Texas Health Presbyterian Hospital.
Duncan, who caught the virus in his native Liberia, died on Wednesday.
The current Ebola outbreak, concentrated in Liberia, Guinea and Sierra Leone, has resulted in more than 8,300 confirmed and suspected cases, and at least 4,033 deaths.
'High-risk procedures'
No details of the health worker's identity or position at the hospital were given, in accordance with family wishes.
Dr Daniel Varga, of the Texas Health Resource, said she had worn a gown, gloves, mask and shield when providing care to Duncan during his second and final hospital admission.
Dr Tom Frieden said there had been a clear breach of protocol. "I think the fact that we don't know of a breach in protocol is concerning because clearly there was a breach in protocol," he told US broadcaster CBS.
The CDC investigation, he told reporters, would focus on possible breaches made during two "high-risk procedures", dialysis and respiratory intubation.
Tests on the infected health worker, he confirmed, would be completed on Sunday.
Mike Rawlings, the mayor of Dallas, said steps had been taken to decontaminate common areas in the patient's apartment complex as well as the patient's car.
Police have been guarding the apartment complex, where a barrel labelled "biohazard" could be seen on a lawn outside.
'Heroic'
The health worker reported a low-grade fever on Friday night and was isolated and referred for testing, officials said. Preliminary test results were received late on Saturday.
Judge Clay Jenkins, chief executive of Dallas County, said the infected health worker was a "heroic person".
"This is obviously bad news, it is not news that should bring about panic," he added.
Duncan tested positive in Dallas on 30 September, 10 days after arriving on a flight from Monrovia via Brussels.
He had become ill a few days after arriving in the US, and went to the Texas Health Presbyterian Hospital in Dallas with a high fever.
