Public Health Director Mercedes Vinuesa told Parliament on Tuesday that authorities were drawing up a list of other people who may have had contact with the nurse so that they can be monitored.
The nurse had helped treat a Spanish priest who died Sept. 25 in a Madrid hospital designated for treating Ebola patients. He had been flown home from Sierra Leone.
She was hospitalized in Madrid on Monday.
Vinuesa said Spain had several therapies available and had begun applying them Monday, but gave no further details.
The nurse, whose name has not been released, was said to be in stable condition.