Authorities say they are looking into how the nurse became infected at a hospital with modern health care facilities.

The 40-year-old nurse is one of some 30 staff in a Madrid hospital who have been treating a priest suffering from Ebola.

The priest died last month after being flown back from Sierra Leone.

西班牙调查女护士感染埃博拉原因The nurse is now in isolation.

Her husband and other members of the medical team are under monitoring.

Antonio Alemay is the head of the primary treatment of the Madrid Region Public Health System.

"We are doing epidemiological vigilance of all the people she has been in contact with and that is to check what contact they had, to check whether all the right protection measures were taken, such as isolation temperature checks for 21 days, twice a day."Meanwhile, the United States is also dealing with its first case of Ebola.

U.S President Barack Obama says the chances of an Ebola outbreak in the country are low.

But the government is working on additional screening protocols for international airline passengers both in the US and overseas.

The Ebola outbreak has left over 3400 dead in West Africa since it began in March.