Three more people have been placed under quarantine for Ebola at a Madrid hospital where a Spanish nurse became infected, while more than 50 other people are being monitored.
The nurse, who cared for a Spanish priest who died of Ebola, is the first case of it being transmitted outside West Africa, where a months-long outbreak has killed 3,500 people.
Her case highlighted the dangers health workers face in caring for Ebola patients. Officials said she had changed a dressing for the priest and collected material from his room after he died.
Dead Ebola victims are highly infectious, and in West Africa their bodies are collected by workers in hazardous materials outfits.
News of the quarantines hit Spain's stock market. It is one of Europe's biggest tourist destinations, and stocks in companies such as airlines and hotel chains fell on the Madrid exchange.
The nurse's husband has shown no signs of having the disease, but was admitted to hospital as a precaution, said Dr Francisco Arnalich, head of internal medicine at the Carlos III hospital where all were under quarantine.
A second nurse who also treated the priest, who died on September 25, was put into quarantine after experiencing diarrhoea, but she did not have a fever, the most common initial symptom for Ebola.
A Nigerian man who recently arrived in Spain is also under quarantine, but tested negative for Ebola in his first examination.
Public health director Mercedes Vinuesa said authorities were drawing up a list of other people who may have had contact with the nurse, who has not been publicly identified.
Authorities have been in touch with 22 people, including relatives and personnel at the hospital in the Madrid suburb of Alcorcon where she went early on Monday with a fever.
They were also monitoring about 30 other members of the health care team that treated Manuel Garcia Viejo, the priest who returned from Sierra Leone and died of the disease.
The health ministry told Cadena SER radio that the nurse was in stable condition and her life not in immediate danger.