Dallas County authorities are anticipating more possible Ebola cases as a second nurse who had treated the first victim of Ebola diagnosed on US soil was infected with the virus, a county official said on Wednesday.

"We are preparing contingencies for more, and that is a very real possibility," Dallas County Judge Clay Jenkins, the county's chief political officer, said at a news conference with other local officials.

Dallas Mayor Mike Rawlings said city officials moved to clean affected areas after the nurse was diagnosed and to alert her neighbours in an apartment complex.

"We rallied together and we decided to move quickly," said Rawlings, adding that he visited the complex earlier Wednesday.

The second nurse infected at Texas Health Presbyterian Hospital, where the first Ebola patient to die in the US was treated, lives alone and has no pets, Rawlings said.

The hospital is doing everything it can to contain the virus, said Dr Daniel Varga of Texas Health Resources, which owns the hospital. "I don't think we have a systematic institutional problem," he said.  - Reuters