A second health worker in the US state of Texas has tested positive for Ebola, health officials say.

A 26-year-old female nurse is already receiving treatment after becoming infected by a Liberian man who died from the deadly virus last week.

The health worker was immediately isolated after reporting a fever on Tuesday, the Texas State Department for Health said in a statement.

The US Centers for Disease Control (CDC) expressed concern over the latest development in a statement, but added that it was "not unexpected that there would be additional exposures", BBC reported.

It has announced new measures to improve hospital preparedness for Ebola treatment, including an immediate response team that will travel to the site of any future Ebola diagnoses to hit the ground "within hours".

Nurses at the Dallas hospital say they worked for days without adequate protective clothing and received little guidance on how to prevent the spread of the virus.