WASHINGTON (AFP) - A second health worker at the Texas hospital where the first case of Ebola contamination on United States soil occurred has tested positive for the disease, the state government said on Wednesday.

The woman's identity was not revealed by the health authorities, who said she came down with a fever on Tuesday and was isolated at Texas Health Presbyterian Hospital Dallas.

A test to confirm the presence of the virus is being done by the Centres for Disease Control and Prevention (CDC).

"This is a heroic person, a person who has dedicated her life to helping others," said Judge Clay Jenkins.

Like the first case, the second concerned a caregiver who treated a Liberian Ebola sufferer who later died at the Dallas hospital, the Texas Department of State Health Services said.

"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 in a statement.

The Centres for Disease and Prevention (CDC) said the second worker's positive test came from a preliminary analysis conducted overnight and the CDC is carrying out its own test to confirm the result.

"As we have said before, because of our ongoing investigation, it is not unexpected that there would be additional exposures," it said in a statement.

Both of the health workers had cared for Ebola sufferer Thomas Eric Duncan, who is thought to have contracted the disease while still in Liberia, and who died on October 8.

The CDC noted it is taking a series of new measures to boost hospitals' preparedness, including sending to Dallas experts who have managed to control Ebola outbreaks in Africa over the past two decades.

The center said it is improving procedures to protect health care workers at the Dallas hospital, and providing health workers there and elsewhere with opportunities for more training.