The Spanish nun, 65-year-old Juliana Bonoha Bohe, was flown to Madrid on Thursday along with 75-year-old Roman Catholic priest Miguel Pajares, who contracted Ebola while helping hospital patients in the Liberian capital Monrovia.
The nun had been cleared of Ebola before leaving Liberia but doctors at Madrid's La Paz-Carlos III hospital repeated the blood test Thursday and said they would do so again in four days.
"The patient has no symptoms, no fever, is well hydrated and in good condition in general," said a medical bulletin from the hospital, where doctors are taking care of the nun and the infected priest in specially equipped isolation rooms.
The nun, whose blood test also came up negative for malaria, is to remain under supervision awaiting the results of further tests, the hospital said.
Spanish health authorities said Thursday that the priest -- the first Ebola victim in the fast-spreading outbreak to be evacuated to Europe -- was stable with no sign of bleeding.
The hospital is not providing medical updates for the missionary, at his request.