A second nurse from Texas who has contracted Ebola told a US health official she had a slight fever and was allowed to board a plane from Ohio to Texas, intensifying concerns about the United States' response to the deadly virus.

The nurse, Amber Vinson, 29, flew from Cleveland to Dallas on Monday, the day before she was diagnosed with Ebola, the US Centers for Disease Control and Prevention said.

Vinson told the CDC her temperature was 37.5 C. Since this is below the CDC's temperature threshold of 38 C she was not barred from flying, a source said.