A nurse in Spain has tested positive for the Ebola virus after treating a patient repatriated to Madrid from Sierra Leone, according to sources within the country's health authorities.

Officials are now waiting for the results of a second test, which if positive would make the nurse the first patient to have been infected with the virus outside west Africa.

The nurse was part of the team attending to a Spanish missionary with Ebola who was repatriated two weeks ago. The 69-year-old missionary, Manuel García Viejo, died just four days after being brought to Madrid's Carlos III hospital.

The nurse arrived at a hospital in Alcorcón with high fever on Monday, said authorities, and the first round of tests tested positive for the deadly virus. Ebola protocol has been put in place while officials wait for the results of a second round of testing.

In August, 75-year-old Spanish missionary Miguel Pajares died in Madrid after being repatriated from Liberia five days earlier. He was the first patient in the current, fast-spreading outbreak to be evacuated to Europe for treatment.

Pajares' repatriation to Madrid prompted concern among health professionals who said that Spanish hospitals were not adequately equipped to handle the Ebola outbreak. Amyts, a trade union that represents physicians, called the repatriation risky, and its president, Daniel Bernabéu, asked Spanish news agency Efe if "anyone could guarantee 100% that the virus wouldn't escape".

Bernabéu compared Spain to the US and pointed out that the Americans have 10 hospitals with the highest level of biosafety possible. Spain, in contrast, has just one suitable hospital with biosafety levels that are much lower.